Worked examples
Two examples
Example 1
At 6 a.m. the temperature was −8°F. By noon it had risen 15 degrees. What was the temperature at noon?
- A rise is positive: −8 + 15.
- First subtract: 15 − 8 = 7. The original larger absolute value is 15, positive.
Answer: 7°F
Example 2
A diver is at −12 meters. She goes down 9 meters more. Where is she now?
- Going down is negative: −12 + (−9).
- Same signs: 12 + 9 = 21, negative.
Answer: −21 meters
Where this is taught: Signed Numbers, Part 9
The drill
Ten problems
How many:
Write each answer as a signed number: a drop, a loss, a debt or a depth below zero is negative. Type the number only; the unit is already there.Write each answer on the line. The answer key, with the reasoning, is on the last page.