The idea
Temperature differences may cross zero, so direction matters.
Follow these steps
- Place both temperatures on a number line.
- Count the distance between them or apply each rise and fall in order.
- Retain the degree symbol and Celsius unit.
See the method in action
Example 1
During which three-hour interval did the temperature rise by the greatest amount?
- The consecutive changes are 13°C, -4°C, 5°C, -2°C, 3°C.
- The greatest rise is 13°C, from 06:00 to 09:00.
Example 2
After rising by 11°C, a temperature is 4°C. What was the starting temperature?
- Subtract the rise from the final reading: 4 − 11 = -7°C.
- Adding 11°C to this starting temperature gives 4°C again.
A useful shortcut
Retain the degree symbol and Celsius unit.
Watch out for these
Three fresh questions
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