Problem 4 · 2017 Math Kangaroo
Easy
Arithmetic & Operations
place-value
Kevin knows that 1111 × 1111 = 1234321. What does he get for 1111 × 2222?
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Answer: D — 2468642
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Hint 1 of 2
2222 is just 2×1111, so 1111×2222 is twice a number you already know.
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Hint 2 of 2
Double 1234321.
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Approach: factor out the 2 and double the known product
- 1111×2222 = 1111×(2×1111) = 2×(1111×1111).
- 1111×1111 = 1234321, so the answer is 2×1234321.
- Doubling gives 2468642 (D).
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