# Advice 1: How to calculate interest on a calculator

To calculate the percentage ofs we have often. For example, to determine the overpayment on the loan or calculate interest on arrears, or to know the gross margins of the company, knowing its turnover and trading margin. Such a lot of tasks in daily life. It would be funny every time to make the proportions and percentages in a column. Moreover, for calculations we do not need a complex programmable calculator.
Instruction
1
Clearly specify the problem statement. We need to find 7% of the number 594.
2
The digits on the calculator number, which is necessary to calculate the interest. In our case, the dialed 594.
3
Click the "X" button. Is - the button for multiplication. Do not confuse it with the " + " button (add).
4
Enter the percent. In our case, type the number 7.
5
Click the "%". This is the letter of interest. More than anything don't type it, no characters "=" (equals). The calculator immediately shows the calculated value. In this case, the figure turned 41,79. Thus, 7% of the number 594 = 41,79.
6
Click "S". This is the reset button, it is highlighted in a different color. The calculator will display zero and you can do the following calculation.
Note
Do not use calculator which works intermittently. Calculator - working tool, the correctness of the testimony which much may depend. Purchase once a good device that will last you for years to come. Reliable calculators are produced by well-known companies producing electronic equipment.
Useful advice
Sometimes check calculate a normal column, not to forget how to count. After all, at hand may not have a calculator. You don't have to get into an awkward situation. Remember that simple calculators built into cell phones.

# Advice 2 : How to solve proportions

The ability to solve proportions can be useful in everyday life. Let's say you have in the kitchen acetic essence with a 40% vinegar, and you need 6% vinegar. Without making the proportions here can not do.
You will need
• pen, paper, analytical thinking
Instruction
1
Write the problem statement. 40% vinegar is 100%, you need to find how much to take of vinegar to obtain a 6% vinegar. It will be H. Recorded two par: 40%=100%, 6%=H.
2
We get the proportion: 40/6=100/x.

Multiply 6 by 100 and divide by 40.
3
Get vinegar essence is 15% of the total water and acetic solution.

It is possible to take 15 ml of vinegar and 75 ml of water to obtain approximately 100 ml of 6% vinegar. About - because water has the property of substitution, and withdrawal of different solutions may yield slightly less than originally planned.
4
The task is more difficult. Is buckwheat flour with a protein content of 12.6 g per 100 g of dry product. And there is a starch with a protein content of 1 g per 100 g of dry product. You need to make the starch-flour mixture with a protein content of 2 g per 100 g of dry product.
5
Take for x the starch content in the mixture in grams, (100-x) content of buckwheat flour in the mixture in grams.
6
Then 1*x/100 - how many grams of protein is necessary for starch 12,6*(100-x)/100 - how many grams of protein accounts for buckwheat flour.

The sum of these fractions is 2 g of protein per 100 g of the mixture.
7
After solving the equation, we find that to obtain a mixture with a content of 2 g of protein we need to take 91 g starch and 9 g of buckwheat flour.

# Advice 3 : How to subtract percentages

A percentage of a number is a hundredth of this number, denoted by 1%. One hundred percent (100%) equal to the number, and 10% of the number equal to a tenth of that number. Under the subtraction percent decrease understand the numbers on what the share.
You will need
• Calculator, paper, pen, skills of oral accounts.
Instruction
1
Turn on the calculator and enter a number N from which you want to deduct a percentage.
2
Press the " - " sign, then dial M percentage you want to subtract and press "%", then press "=". As a result, you will receive a number that is less than the number N by M percent.
3
If you don't have a calculator, divide the number N by 100. So you will receive the part number, which is 1 per cent. Next, the resulting, after dividing, multiply by the number M. as a result, you will receive a part of the number K, which accounts for M%. Then subtract from the initial number N number K, which is equal to M percent of the number N. the result of subtraction, you will receive a number that is less than N by M percent. That is, you deduct from the number a fraction of a percent.
Note
The percentage deducted may not exceed the value of 100. The interest rates vary from zero to one hundred.
Useful advice
The same way you can to a number and to add interest. To do this, instead of the key with the sign "-", press the "+"sign.

# Advice 4 : How to calculate interest on a calculator

To calculate the percentage ofs we have often. For example, to determine the overpayment on the loan or calculate interest on arrears, or to know the gross margins of the company, knowing its turnover and trading margin. Such a lot of tasks in daily life. It would be funny every time to make the proportions and percentages in a column. Moreover, for calculations we do not need a complex programmable calculator.
Instruction
1
Clearly specify the problem statement. We need to find 7% of the number 594.
2
The digits on the calculator number, which is necessary to calculate the interest. In our case, the dialed 594.
3
Click the "X" button. Is - the button for multiplication. Do not confuse it with the " + " button (add).
4
Enter the percent. In our case, type the number 7.
5
Click the "%". This is the letter of interest. More than anything don't type it, no characters "=" (equals). The calculator immediately shows the calculated value. In this case, the figure turned 41,79. Thus, 7% of the number 594 = 41,79.
6
Click "S". This is the reset button, it is highlighted in a different color. The calculator will display zero and you can do the following calculation.
Note
Do not use calculator which works intermittently. Calculator - working tool, the correctness of the testimony which much may depend. Purchase once a good device that will last you for years to come. Reliable calculators are produced by well-known companies producing electronic equipment.
Useful advice
Sometimes check calculate a normal column, not to forget how to count. After all, at hand may not have a calculator. You don't have to get into an awkward situation. Remember that simple calculators built into cell phones.

# Advice 5 : How to calculate percentage in mathematics

With the need to calculate the percent of people faces constantly, sometimes even without realizing it. And not only on the math, but, for example, trying to determine what part of total family income to make utility payments or payment for a kindergarten. And many need to count the percent baffled.
Instruction
1
Understand that the number from which to calculate percentages is always one hundred percent. Regardless of whether it is in the problem or you found it, adding the income of all family members. It can be described, for example, the letter a or any other letter, and you do not designate.
2
Find that number 1 percent. For this original number, divide by 100. If we take the General formula, 1 percent of the number and will be equal to a/100.
3
Suppose you want to find not 1 percent and 20. Then the number which designated 1 percent of the specified, must be multiplied by the required percentage. That is, will a/100*20. For example, your salary is 11 000 rubles. 1% of this number is 110 rubles, and 20% -2 200 rubles.
4
For example, the problem is to know how many percent of the original number a is number b. The amount of interest that you want to find, label as X. Find 1%, which will be a/100. In order to determine how many percent of the number a is number b, it is necessary to divide it into the value. Remember the rule of dividing the whole number into a fraction. Need the number to divide into the numerator of the fraction (in this case a) and multiply by its denominator (in this case, 100): x=b/a*100. For example, at the warehouse brought 250 bags of potatoes. 35 storekeeper immediately sent to the store, and he needed to know how much it amounts to per cent of the total number of bags. Find 1% which in this problem will amount to 250/100=2.5 bag. Dividing 35 by 2.5, you get the desired amount to 14%.
Note
Before you take on the task of interest, remember the rules of multiplying and dividing fractions.
Useful advice
When calculating interest, you can use the calculator. But you can experience infinite decimal fraction. It must be rounded.

# Advice 6 : How to solve problems on proportions

Leaves no doubt that the proportions of the thing desired. The proportions in our lives everywhere. Calculate salary for the year, knowing the monthly income. How much to buy of goods for money, if you know the price. It's all proportions.
Instruction
1
When solving problems on proportions is always possible to use the same principle. That they are comfortable. When dealing with proportion, always proceed as follows:Define the unknown and label it with the letter H.
2
Record the condition of tasks as a table.
3
Determine the type of dependence. They can be direct or reverse. How to determine the type? If the proportion is subject to the rule "the more, the better", so a direct relationship. If on the contrary, "the more, the less", it means an inverse relationship.
4
Put your hands with the edges of the table in accordance with the type of dependency. Remember: the arrow pointing upwards.
5
Using the table, write a proportion.
6
Solve the proportion.
7
Now let us examine two examples of different types of dependence.Task 1. 8 yards of cloth cost 30 R. How much are the 16 yards of this cloth?
1) the Unknown - the cost of 16 yards of cloth. Let's denote it as x.
2) let's Make the table:8 yards 30 p.
16 yards x R. 3) to Define the type of dependency. Think: the more cloth you buy, the more you will pay. Therefore, a direct relationship.4) Put the arrow in the table:^ 8 yards 30 p. ^
| 16 yards R. x |5) we form the ratio:8/16=30/xx=60 p answer: the cost of 16 yards of cloth is 60 p.
8
Task 2. The motorist noticed that at a speed of 60 km/h he drove a bridge across the river for 40 s. On the way back he passed the bridge in 30 s. Determine the speed of the car on the way back.1) the Unknown - the speed of the car on the way back.2) let's Make the table:60km/h 40
x km/h 30 C3) Define the type of dependency. The greater the speed, the faster a motorist will pass a bridge. Hence the inverse relationship.4) will form the proportion. In the case of inverse relationship here a little trick: one of the table columns you need to flip. In our case, we get the following proportion:60/x=30/40x=80 km/cotvet: back on the bridge a motorist drove at speeds of 80 km/h.
Useful advice
A direct correlation obeys the rule of "the more, the better".

Reverse obeys the rule of "bigger is less."

In the case of reverse dependencies when preparing the proportions of one of the columns of the table should turn.

# Advice 7 : How to calculate a percentage of the amount

The percentage in Latin ("pro centum" means one-hundredth. So if you want to find a certain percentage of a certain amount of money, it means that it is necessary to determine how many hundredths of the sum contains the specified percentage. If in mind to not count it turns out, the easiest way to calculate a percentage using a calculator.
Instruction
1
Use to calculate the percentage of a given amount, for example, the standard calculator Windows. Link to his start-up can be found in the main menu system - open it by pressing WIN key or click the mouse on "start" button. You need to go to "All programs" to reveal in this subsection "Standard" and click the string "Calculator." However, hackers are not a fan of "mouse computing" and if you also want to feel like a little hacker, then press the key combination WIN + R, type calc and press Enter. Both run the same Windows calculator.
2
Keep the number ofyour equivalent of the available amount of money. This operation can also be performed with the mouse, and only keyboard - right buttons of the calculator interface duplicate the same keys on the keyboard.
3
Find one hundredth part of the number entered. To do this, use the key with a slash (slash) on the keyboard interface on the screen, and then enter the number 100.
4
Multiply a hundredth of the amount to a known amount of interest. To do this, press on the keyboard or click the mouse on the screen the button with the asterisk, and then type the percentage.
5
Complete the calculation of the percentage of the amount by tapping on the keyboard or clicking on-screen buttons with the sign of equality. The calculator will show you the numeric expression specified percentage of the amount entered.
6
Having access to the Internet for solution of this problem you can do without a calculator. In the network there are many analogues that allow us to make the required calculations directly in the browser window. If there is no time to search for and develop such online services, then enter the desired mathematical expression directly in the query box of Google search engine and immediately get a result. For example, to calculate 13% from the sum of 25 thousand 512 rubles 14 kopecks, enter the following query: "25521,14 / 100 * 13".
Note
How to calculate percentages. In everyday life often need to be able to determine what percentage of a particular number from the integer part. It is a mathematical action that are in high school, could come in handy in the case of the calculation of various loan repayments, calculate ratios for any purchases, and only on the job regularly has to use comparative characteristics, expressed in percent.
Useful advice
How to calculate percentages? 4 APR 2012. Category: Training. No comments. Surely you are not just faced with such a thing as "percentage". And some even required it to count. The first way is to calculate in mind: the Number from which you want to find the percentage you need to divide by one hundred and then multiply by the percentage. Or just multiply the number by the percentage expressed in hundredths (percent divided by one hundred). For example, we need to find 28% of the 924.

# Advice 8 : How to divide a percent

A cent is one hundredth part of any initial value. This ratio, i.e. a relative measure with no dimension (rubles, pieces, liters, etc.). In addition to simple operations finding percent of sometimes necessary to produce more complex - for example, the division of percent share of.
Instruction
1
If the result of the operation of dividing the value expressed by percent to any number necessary to obtain the amount of interest (i.e., relative value), nothing special compared to dividing regular numbers to do not required. Just divide the percentage by the given number, ignoring the % sign, and add to the resulting number. For example, if you want to determine how much interest will remain, if you divide 65% off for ten parts, the result will be 6.5 per cent.
2
If the result of the division need to get the number in some specific units (i.e. absolute value), we described in the previous step, the operation should be supplemented by finding the percentage of the original value. For example, suppose you want to determine the absolute value of the bags, if 65% of the initial amount of twenty thousand pieces of sack tare divided into ten equal parts. In this case, first divide 65% by 10 (the result is 6.5%) and then proceed to the calculation of the percentage of the original amount.
3
For finding the absolute value of the share expressed in percent, can be used several ways. The first is to find how many absolute units (in this case, bags) accounting for one percent, and then multiplied by the value of the share is in percent. That is, for example, 20000/100*6,5=1300 bags. Another way is to multiply the original number, expressed in absolute units by a factor which is a divided by 100 share in percentage (6,5/100=0,065). That is 20000*0,065=1300 bags. For practical calculations it is possible to use a calculator or, for example, the built-in search engine Nigma calculator. To calculate the absolute value of one tenth of the share of 65% of the original quantity of 20,000 bags enter on the website of the system, the request 20000/100*(65/10) and click "Search". The search engine will calculate and show the number 1300.

# Advice 9 : How to make override

Override is a special kind of estimates, which contains information about executed works. It is calculated the percentage ratio between the volume of work performed and the full scope of throughout the estimate. The procedure for filing and completing the override is determined by the Resolution of Goskomstat of the Russian Federation No. 71A from 31.10.1997.
Instruction
1
Use to compile override the acts of the executed works accounting forms KS-2, KS-3, and in some cases KS-6A, as well as the forms provided by the contractor.
2
Apply before the override information, which contains information about the written off materials expended in the performance of works. It should also be noted what equipment was installed at the facility, and to provide copies of documents of installed equipment. Sometimes it so happens that the contractor attempts to inflate the amount so you should carefully check all the supporting documents.
3
Start preparing for the compilation of the override for a few weeks before the deadline, ideally start to work on it immediately after the signing the previous one. Make a plan and projects that need to be performed in the current reporting period to prepare the source data.
4
Visit the facility, check the current status of the work. Remember that for incorrect statements lay the blame on you, not the superintendent or the superintendent. Collect a complete and adequate basis for the compilation of the override.
5
Fill in the required customer and contractor forms to override. For the cost estimates or make the distribution of information on volumes of close work. Show the amount of work the technical supervision, which should be representative for the object and indicate the points that are specified in the override. Will receive from tüv confirmation of a writ of execution of these volumes.
6
Close all orders. Tell the contractor the certificate obtained in the technical supervision of performed works, which confirms the data override. The last step will be reporting to the customer. It is necessary to fully prove the amount of work done, otherwise he may refuse to sign written override.

# Advice 10 : How to find how many percent is the number

One hundredth part of some quantity in mathematics is called a cent. Usually a percentage of the numbers used for a visual comparison of a shares in relation to the whole. Indicators expressed in percentage, are considered to be relative, that is, showing the magnitude of one number relative to another. This implies that for interest calculation you need to know two numbers - compare and with which it is compared.
You will need
• - optional: Internet access
• - optional: computer or calculator.
Instruction
1
Determine which of two numbers should be taken as 100%. In statistics this number is called the "baseline" is the whole, the share of which in percents you need to find. For example, if you used last month, Internet traffic was 12.5 GB, and for the first week of a new month is 3.7 GB, then the baseline should be the number of 12.5.
2
Find the ratio between the share and the whole, that is, between the comparison and baseline indicators. If you use example data from the previous step, this should be the attitude of 3.7 GB to 12.5 (3.7 V / 12,5 = 0,296).
3
Increase calculated in the previous step the number a hundred times. The resulting value will Express compare the percentage from the base. For example, 0,296*100=29.6% of the means spent for the first week of the month to 3.7 gigabytes of Internet traffic 29.6% of all traffic last month (12,5 GB).
4
Use onlinecalculators as the easiest way of calculating interest, if you count "in mind" does not work. To solve this problem to find the corresponding service in the network not necessarily - some search engines have built in calculators. For example, to calculate the percent used in the previous steps of the sample, go to Google and in the search query box enter 3,7/12,5*100. Search engine calculate the value and show the answer (29,6).
5
If access to the network, you can use any calculator, including the one that is installed in the computer along with the operating system. If the operating system is Windows, then find the link to this application can run in the main menu. Press the Windows key to expand it. If you have a version of Windows 7, then type "cal" and click "Calculator" in the search results. In other versions of Windows go to "All programs", then to "Standard" and in the section "Service", click "Calculator". The interface of this app is very simple, so the operation of division and multiplication you should not cause difficulties.

# Advice 11 : How to calculate mass percent

Mass percent is the ratio of the mass of any component of the solution, alloy or mixture to the total weight of the substances in this solution, expressed in percentageAh. The higher the percentage, the more the content of a component.
Instruction
1
Remember the task set before the great scientist Archimedes king Hieronim, and slightly modify it. Suppose Archimedes found that the roguish goldsmith had stolen some of the gold, replacing it with silver. As a result, the alloy from which were made the Royal crown, consisted of 150 cubic centimeters of gold and 100 cubic centimeters of silver. Task: find the mass percentage of gold in the alloy.
2
Remember the density of these precious metals. 1 cubic cm of gold contains 19.6 grams of 1 cubic cm of silver is 10.5 grams. To simplify, you can round these values to 20 and 10 grams, respectively.
3
Next, perform the calculation: 150*20 + 100*10 = 4000 gram, that is 4 pounds. This is the alloy used for fabrication of the crown. Since the problem says nothing about the "waste" will get the response: 150*20/4000 = 3/4 = 0,75. Or in another way, 75%. That was the mass percentage of gold in a supposedly "pure gold" the crown of Hiero.
4
And if you were dealing with a solution? For example, you have been given this task: to determine the mass percentage of salt (sodium chloride) in it dvuhosnom solution.
5
And there is absolutely nothing complicated. Remember, what is the molarity. This is the number of moles of substance in 1 liter of solution. Mol, respectively, the amount of a substance whose mass (in grams) equal to its mass in atomic units. You have only to write the formula of common salt, and learn a lot of its components (in atomic units), looking at the periodic Table. The mass of sodium is 23.e.m. the mass of chlorine is 35.5.e.m. The amount you get of 58.5 grams/mol. Accordingly, the mass of 2 moles of salt = 117 grams.
6
Therefore, in 1 liter of 2M aqueous solution of sodium chloride contains 117 grams of the salt. What is the density of this solution? According to the table of densities, find that it is approximately equal to 1.08 g/ml. Therefore, in 1 liter of this solution will contain about 1080 grams.
7
And then the problem is solved in one step. By dividing the mass of salt (117 grams) the total weight of the solution (1080 g), we get: 117/1080 = 0,108. Or in the percentage ofOh is 10.8%. This is the mass percentage of salt in its 2M solution.
Note
Mass percentage of sodium chloride will remain unchanged, regardless of the number of the solution.
Useful advice
When solving the problem with the gold alloy you used the rounded value of the density of gold and silver. If you want more precision, this is unacceptable.
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