AlgebraMediumTime for a candle to reach half its height
Algebra practice question
A candle is 20 centimetres tall and burns down at 1.5 centimetres per hour. After how many hours will the candle be half its original height?
Answer: 20/3 or 6.67
Half the height is 10 cm, so it must burn 10 cm: 10 ÷ 1.5 = 20/3 hours.
Common wrong answers
- If you answered 10
- 10 is the height to burn, in centimetres, not the time.
- If you answered 15
- 15 is 10 × 1.5, multiplying instead of dividing.
- If you answered 13.33
- 13.33 is the time to burn completely.
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