Advanced MathMediumRepeated halving to reach a target
Advanced Math practice question
A cup of coffee cools so that its temperature above room temperature halves every 8 minutes. If the coffee starts 64°C above room temperature, after how many minutes will it be 4°C above room temperature?
Answer: 32
64 → 32 → 16 → 8 → 4 takes four halvings, and 4 × 8 = 32 minutes.
Common wrong answers
- If you answered 4
- 4 is the number of halvings, not the minutes.
- If you answered 16
- 16 is two halvings, reaching 16°C above.
- If you answered 128
- 128 divides 64 by 4 and multiplies by 8, mis-structuring the halving.
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