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Quick Check
A scuba diver uses negative numbers to represent her depth below sea level. She started at the depth
5 2
of −1 meters. Then she dove down to a depth of −4 meters. 0
10 10
Complete the following statements.
–1
1. To find the difference between those depths, the operation used is ...................... . 5
−1
2  5  10
−4 ..................  −1  –2
10  10 
2. To subtract means to ...................... its opposite.
2  5  2 5 –3
−4 ......................  −1  = −4 ................. 1 = .................... .
10  10  10 10
3. Locate the difference in depth (....................) on the number line. –4 −4 2
10
Start from ...................... move ...................... units reach ...................... .
–5
This is the total distance that the diver dove to reach her new depth.

Practice Time 3C

1. Add the following rational numbers.

8 − 7 13  − 15 −7 5 3 − 8
(a) + (b) +   (c) + (d) +
13 13 − 48  48  22 11 − 5 15

2. Subtract the following rational numbers.
5
 −  4 5  1   − 7  7  −  11 2
− 
(a)   11   − 11 (b)   − 8  −  8   (c)   5  −   −11   (d) 12 − 1 18


3. Simplify the following.
5
 −  9  −13   −   1   − 4  − 7
(a)   20   −   32   +   −28   (b)   − 12  −  15 −   18  


8  − 7  3 
(c) +   −  
19  76   − 38
4. The sum of two rational numbers is −7 . If one of the numbers is 15 , find the other.
8 8
5. The sum of two rational numbers is 5 . If one of the numbers is 4 , find the other.
6 9
6. What should be added to 11 to get −13 ?
15 20
−5 −7
7. What should be subtracted from to get ?
9 18
 8 − 11 11  5 − 5
8. What should be added to  9 + 6 − 18  to get  12 + 18 ?




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