Question

Which correctly gives the expression using addition? –17.9 – 4.2

a. –17.9+4.2
b. 17.9+4.2
c. –17.9+(–4.2)
d. 17.9+(–4.2)

Answer 1

c. –17.9+(–4.2)

The General rule for adding and subtracting numbers
1. Two integers with the same signs
Once 2 integers has the same sign, then just add the numbers.
For example
1. 1+1 = 2
2. 2 + 5 = 7

2. Two integers with different signs
When 2 integers has different sign, then find the difference
For example
1. 1-1 =0
2. 2 – 5 = -3

3. Two integers that vary in sign
When 2 integers vary in sign, then it will depend who which number carries the largest value
For example
1. -3 + 2 = -1
2. 2 – 1 = 1