Problem 2 · 2009 Math Kangaroo
Easy
Number Theory
last-digit
Which of the following numbers is even?
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Answer: D — 200 × 9
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Hint 1 of 2
A number is even when its value ends in an even digit — work out each option's value.
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Hint 2 of 2
Multiplying anything by an even number gives an even result.
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Approach: evaluate each option
- 2009 is odd; 2+0+0+9 = 11 is odd; 200−9 = 191 is odd; 200+9 = 209 is odd.
- 200 × 9 = 1800, which is even.
- So the even one is 200 × 9 — answer D.
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