ISEE Mathematics Achievement Question 9: Answer and Explanation
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Question: 9
9. If the sum of the integers from 1 to 499, inclusive, is r, what is the sum of the integers from 1 to 497, inclusive, in terms of r ?
- A. r – 499
- B. r + 499
- C. r – 997
- D. r + 997
Correct Answer: C
Explanation:
C
The sum of the integers from 1 to 497 will not include two numbers counted in the sum of all integers from 1 to 499, namely, 498 and 499. If the sum of all integers from 1 to 499 is r, then the sum of all integers from 1 to 497 will be r minus the sum of 498 and 499: r – (498 + 499), or r – 997.