What is the minimum number of integers which must be removed from the first 50 positive even integers so that the sum of the remaining integers is ?
Solution
The first even positive integers are , and their sum is . To reduce the sum to we must subtract . The average of the numbers removed must be less than , so we need to remove at least six. To use as few numbers as possible, we first remove the five largest numbers from down. Now , which is nearly there, so to bring the total subtracted to we finally need to remove .
[There are, of course, many other combinations of five integers with a sum of that can be removed. ]
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