By following these two simple steps, we will be able to evaluate all addition and subtraction mathematics expression.
1. Find out all the terms and signs in the expression:
Example :
-7+8
The terms identified here are -7 and +8
For term [-7] => sign is '-', number is '7'
For term [+8] => sign is '+', number is '8'
2. Proceed with two terms and compare the signs of the terms.
Check if the two terms have the same sign?
If SAME :
=> Final number is the sum of the two numbers
=> Final sign is the sign of the two terms
If DIFFERENT:
=> Final number is the difference between the two numbers
=> Final sign is the sign of the bigger number
Example 1:
-7+8
Is the sign for the two terms the same? [-7] and [+8]
Ans : No.
What is the difference between the two numbers 7 and 8?
Ans : 1
What is the sign of the bigger number (-7 and +8)?
Ans : +
Result of -7 +8 = +1
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Lets work through more examples.
Example 2:
-2-9
1. The terms are [-2] and [-9]
For term [-2] => sign is '-', number is '2'
For term [-9] => sign is '-', number is '9'
2. Compare [-2] and [-9].
Are the two terms having the same sign?
Ans : Yes
=> Final number is sum of 2 and 9, which is 11
=> Final sign is '-'
Result of -2 -9 = -11
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Example 3:
-5+10
1. The terms identified are [-5] and [+10]
For term [-5] => sign is '-', number is '5'
For term [+10] => sign is '+', number is '10'
2. Compare the two terms [-5] and [+10]
Are the two terms having the same sign?
Ans : No.
=> Final number is difference of 5 and 10 , which is 5
=> Final sign is the sign of the bigger number. In this case, the bigger number is 10, sign is '+'
Result of -5 +10 = +5
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Example 4:
6-18
1. The terms identified are [+6] and [-18]
For term [+6] => sign is '+', number is '6'
For term [-18] => sign is '-', number is '18'
2. Compare [+6] and [-18].
Are the two terms having the same sign?
Ans : No.
=> Final number is the difference of the two number 6 and 18 , which is 12
=> Final sign is the sign of the larger number. In this case, the sign of the larger number is '-'
Result of 6-18 = -12
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To help visualize the flow:
