Advice 1: How to subtract a percentage of the amount

Often in life we have to use simple mathematical operations quickly and without the aid of electronic calculators. For example, the calculation of wages should be deducted from the total monetary amount of thirteen percent. How to do it? After subtracting different types of numbers can not, without a certain conformity between them. And it can be done, knowing a number of simple actions.
How to subtract a percentage of the amount
For starters, the number, expressed as a percentage, translates into the same meaning that it has a total deductible amount. This is solved the proportion: the sum total is one hundred percent, but an unknown amount is the percentage. "Unknown amount" is the translated value, which will need to deduct from the total amount. If you write the members of the proportion below each other, respectively, it is easy to understand the principle of its decision: "criss cross". That is, the cross lying known members are multiplied and the product divided by the member, not having a pair. Example. May need to calculate a deduction of thirty-five percent of the amount of income equal to one hundred and fifty rubles. Is made proportion: 150 rubles - 100% of "x" rubles – 35 %. "X" rubles = (150 rubles*35%)/100%=52.5 ruble.
After finding the deducted value deducted from the total amount found expression. The difference is the solution of the problem. Example. Of the total income equal to one hundred fifty rubles to take thirty five percent, constituting fifty-two and a half rubles. It turns out, 150-52,5=97.5 rubles.

Advice 2 : How to find the percentage difference of numbers

The percent is called a relative unit that expresses a proportion of the total of the whole, divided into one hundred equal parts. Since it is a relative unit, it gives the opportunity to compare non-comparable, it would seem that measurement - for example, you can compare the difference between milk yields of Australian and Norwegian cows with the difference in the number of Sunny days in these countries. The calculation of the percentage difference of two indicators - the operation is not difficult, but having some special features.
How to find the percentage difference of numbers
Before proceeding to calculations, determine which of the numbers should be taken as 100%, i.e., determine the "baseline". For example, in terms of the weight characteristics of the component parts of rocket fuel: 6 tons of kerosene and 4 tons of oxidizer. Then for 100% you can take the total weight (10 tons), it is possible to compare the amount of oxidizing agent relative to kerosene (100% = 6 tons), and it is possible for the baseline to take the weight of the oxidizer (100% = 4 tons). In each case, a percentage difference between the original values in relative units will give different values.
Use the baseline defined in the first step to find out how much percent per absolute unit. For example, if in the example above, 100% were accepted total weight (6+4=10), each absolute measurement unit (ton) would have 100/10=10 relative units (percent). If the baseline is adopted, the weight of the oxidizer, each ton will correspond to 100/4=25%, but if kerosene is 100/6≈16,67%.
Find the difference between the compared quantities in absolute units. This value does not depend on the baseline and is determined by the usual operation of subtraction. For the above example, whatever you took for one hundred percent, the difference will be equal to two tons, but when compared relative to kerosene this value will be negative: 4-6=-2.
Put the difference of the absolute values (tonnes) relative units (percentages). Obtained in the previous step, the number and multiply by the value obtained in the second step. In our example, this means that the difference of weight of components in tonnes (2) should be multiplied by the amount of interest attributable to each ton. If the base figure were accepted the total weight of the fuel, multiply, should 10%: 2*10%=20%. If the comparison is relative to the weight of the oxidizer, then the multiplier must be equal to 25% (2*25=50%), but if the base rate - a weight of kerosene, 16,67% (-2*16,67=-33,34%).
If you need to submit a formula calculation in a General way indicate the initial value, for example, the letters X and Y, and the interest difference - by the letter p. Then the calculation formula of the amount of the original values would be: p=|X-Y|*100/(X+Y). For calculations on a variable, X in this formula, it is necessary to change so: p=(Y-X)*100/X, and with respect to the variable Y the formula is: p=(X-Y)*100/Y.
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