AlgebraHardTime to reach zero from two readings
Algebra practice question
A candle was 45 centimetres tall when lit and 15 centimetres tall after 6 hours, burning at a constant rate. After how many hours from lighting will it burn out completely?
- A. 9Correct
- B. 8
- C. 15
- D. 3
Answer: A. 9
Rate: 30 cm in 6 hours is 5 cm per hour. 45 ÷ 5 = 9 hours.
Why the other answers are wrong
- B. 8
- 8 hours leaves 5 cm.
- C. 15
- 15 is the height after 6 hours, not a time.
- D. 3
- 3 hours is the time to burn the last 15 cm, not the total.
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