Problem 5 · 2015 Math Kangaroo
Easy
Arithmetic & Operations
arithmetic-series
If you add all the whole numbers from 2001 to 2031 and then divide the sum by 31, you get:
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Answer: D — 2016
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Hint 1 of 2
The numbers 2001 to 2031 are evenly spaced, so their average is the middle one.
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Hint 2 of 2
There are 31 of them — the same 31 you divide by.
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Approach: average of an evenly spaced list is the middle value
- From 2001 to 2031 there are 31 numbers, evenly spaced, so their average is the middle one, 2016.
- Their sum is 31×2016, and dividing by 31 gives back 2016 (D).
Mark:
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