AlgebraVery hardTime until a falling quantity reaches zero
Algebra practice question
A candle is 40 centimetres tall and burns down at 2.5 centimetres per hour. After how many hours will it be completely burnt?
Answer: 16
40 − 2.5t = 0 gives t = 16.
Common wrong answers
- If you answered 8
- 8 halves 16.
- If you answered 10
- 10 uses 4 centimetres per hour.
- If you answered 100
- 100 multiplies 40 by 2.5.
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