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Interview prep / Brainteaser/Logic

Weight of berries after drying from 99% water

Question

A 100100 kg batch of berries is 99%99\% water by weight. After drying, water makes up 98%98\% of the weight. What do the berries weigh now?

Short answer

5050 kg. The dry matter is 11 kg and does not change. After drying it is 2%2\% of the total, so the total is 1/0.02=501/0.02=50 kg.

Adapted from Wilmott, Frequently Asked Questions in Quantitative Finance, ch. 10 brainteaser '100 kg of berries', p.353; question and answer rewritten by SelfMadeQuant.com.

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