Puzzle of the day · No. 4 · 16 October
Five stars for the café
Schulz’s café is rated 4.5 from 20 reviews. How many five-star reviews in a row does it need for the rating to reach 4.8?
Answer: 30. The ratings add up to 90 now. After n five-star reviews the average (90 + 5n) / (20 + n) must be 4.8. That gives 0.2n = 6, n = 30. Each new five moves the average less and less: the higher the rating, the dearer every tenth.
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