Advice 1: How to solve examples with cons

Still in elementary school are taught how to add and subtract numbers. In order to learn how to do it, you need to learn the table of addition and based on it the table of subtraction. So, the graders will deduct nine of the seventeen or to solve any example. However, to lead to a dead end it will reverse example: how to subtract nine from seventeen. Examples with negative numbers given in the school curriculum much later, when the person Matures to abstract thinking.
How to solve examples with cons
Mathematical operations there are four types: addition, subtraction, multiplication, and division. Therefore, examples of the cons will be four types. Negative numbers within the example brackets in order not to confuse the mathematical operation. For example, 6-(-7), 5+(-9), -4*(-3) or 34:(-17).
Addition. This action may take the form of:1) 3+(-6)=3-6=-3. Replacement steps: first disclosed the brackets, the + sign changes to the opposite, then from the larger (in absolute value) of the number "6" is subtracted least - "3", then the answer will receive a mark greater, that is "-".
2) -3+6=3. This example can be recorded differently ("6-3") or to decide on the principle of "from greater to take less and to give the answer the sign more."
3) -3+(-6)=-3-6=-9. When opening brackets are replaced operations of addition subtraction, then summarizes the modules of the numbers and results put a minus sign.
Subtraction.1) 8-(-5)=8+5=13. Disclosed brackets, the sign of the action is reversed, it turns out the addition.
2) -9-3=-12. Sample elements are summarized and an overall "- "sign.
3) -10-(-5)=-10+5=-5. When opening brackets again changed the sign to "+", then from the larger number subtracted from smaller and have the answer - the sign of the larger number.
Multiplication and division.When performing multiplication or division sign doesn't affect the action itself. If you work or divide numbers with different signs the answer is assigned a minus sign, if the numbers with the same signs, the result is always the sign "plus".1)-4*9=-36; -6:2=-3.
2)6*(-5)=-30; 45:(-5)=-9.
3)-7*(-8)=56; -44:(-11)=4.

Advice 2 : How to add only positive numbers

If necessary, add up to only a positive or only negative numbers, you can sort them depending on the sign and then to implement the operation of addition. But if the array is large or the operation has to be repeated frequently, this procedure usually trust programs compiled using any of the programming languages. The table editor Microsoft Office Excel allows to solve this problem without programming knowledge.
How to add only positive numbers
You will need
  • The table editor Microsoft Office Excel
Start Microsoft Excel and type in an empty cell of the table an array of values positive number which needs to be folded. This can be done manually, but if it is possible to copy all the array data in text format, it will be much easier to insert it into the table, pre-slightly changing the format. If the number in the text containing the source values, separated by spaces, then perform with any text editor replace all spaces with tabs. After this operation, copy the text numbersand paste it into Excel - numbers will be placed in the cells of one row. If you replace the spaces with the signs of the end of the row, when you paste in spreadsheet editor numbers will line up in the column.
Enter the formula that performs the summation of the range of cells with pre-specified test conditions. To do this, select the table empty cell in which you would like to put the result of the calculation, and click the icon insert function - it is in the beginning of the formula bar above the table. This way you start the function wizard, which helps make up the formula online.
Open the drop-down Category list and select "Math". In the list of functions this section to find the one which is called SUMIF - click it and click "OK" to proceed to the next step.
Specify arguments that should be passed to this function. First in the field "Range" you have to specify the start and end cell of the entered data. The easiest way to do this by highlighting the entire cell range with the mouse - in this case, the wizard will enter the desired values in the appropriate field. Then under Criteria, specify the condition that the formula shall select sum values. For addition of positive numbers, set the criteria to >0 and press the tab key. The third field ("Diapazonului") leave blank.
Press "OK" and Excel will put in the cell the formula is designed to calculate the value in accordance with it.
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