Problem 4 · 2009 Math Kangaroo
Easy
Number Theory
divisibility
Mari, Ville and Ossi are going to a coffee shop. Each of them has 3 glasses of juice, 2 cups of ice cream and 5 biscuits. What value could the total bill come up to in the end?
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Answer: C — €37.20
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Hint 1 of 2
Each of the three orders the same things, so the bill is three identical orders added up.
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Hint 2 of 2
That makes the total a multiple of 3—check which price is divisible by 3.
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Approach: the total is three equal orders, hence a multiple of 3
- Three people each buy 3 + 2 + 5 items, so the bill is 3 × (one person's order).
- Therefore the total must be divisible by 3.
- Of the choices only €37.20 (3720 cents) is divisible by 3, so the bill is €37.20.
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