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A body cools from 40 deg C to 36 deg C in 5 minutes in surroundings at a constant 16 deg C. How long does it take to cool further from 36 deg C to 32 deg C?

1. 5 min
2. 5.5 min
3. 6.1 min
4. 7 min

Correct answer: 6.1 min

Solution

First stage: 4/5 = k(38-16). Second stage: 4/t = k(34-16). Solving gives t about 6.1 min.

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