Problem 7 · 2025 Math Kangaroo
Easy
Arithmetic & Operations
order-of-operations
Ohad wants to write the four digits 2, 0, 2 and 5 in the four boxes of the calculation shown. What is the smallest result Ohad could obtain?
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Answer: C — −5
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Hint 1 of 2
You want the result of □ − □ + □ − □ as small as possible.
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Hint 2 of 2
Put the biggest digits where they are subtracted and the smallest where they are added.
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Approach: place digits to minimise the signed sum
- The expression is (1st + 3rd) − (2nd + 4th); minimise it by making the added pair small and the subtracted pair big.
- Add the two smallest, 0 and 2; subtract the two largest, 5 and 2.
- Best value: \(0 + 2 - 5 - 2 = -5\), which is (C).
Mark:
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