Problem 1 · 2009 Math Kangaroo
Easy
Number Theory
divisibility
Which of the following is an even number?
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Answer: D — 200 × 9
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Hint 1 of 2
An even number is a multiple of 2 - in a product, one factor of 2 is enough.
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Hint 2 of 2
Evaluate each choice and pick the one that comes out even.
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Approach: evaluate each option and test for even
- 2009 is odd; 2+0+0+9=11 is odd; 200-9=191 is odd; 200+9=209 is odd.
- Only 200x9=1800 is even, since 200 already carries a factor of 2.
- So the even number is 200 x 9.
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