Problem 13 · 2021 Math Kangaroo
Medium
Arithmetic & Operations
unit-ratework-backward
In an ice cream shop there is some money in a drawer. After 6 ice creams were sold, there were 70 euros left in the drawer. After a total of 16 ice creams were sold, there were 120 euros left in the drawer. How many euros were there in the drawer at the start?
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Answer: C — 40
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Hint 1 of 2
Between the two moments, 10 more ice creams were sold and the drawer grew by 50 euros.
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Hint 2 of 2
Find the price of one ice cream, then step back to before any were sold.
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Approach: find the price per ice cream, then work back to the start
- From 6 to 16 sold is 10 more ice creams, and the money rose from 70 to 120, i.e. +50 euros.
- So each ice cream costs 50 / 10 = 5 euros.
- The first 6 brought in 6 x 5 = 30 euros, so the start amount was 70 - 30 = 40 euros.
- So there were 40 euros at the start (C).
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