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If A equals

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If A equals

by REINE » Wed Mar 22, 2017 12:26 am
If A equals the sum of the even integers from 2 to 20 inclusive and B equals the sum of the odd integers from 1 to 19 inclusive, what is the value of a- b.
A. 1
B.10
C. 19
D. 20
E. 21
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by Brent@GMATPrepNow » Wed Mar 22, 2017 7:39 am
REINE wrote:If A equals the sum of the even integers from 2 to 20 inclusive and B equals the sum of the odd integers from 1 to 19 inclusive, what is the value of a- b.
A. 1
B.10
C. 19
D. 20
E. 21
A: 20 + 18 + 16 + . . . + 4 + 2
B: 19 + 17 + 15 + . . . + 3 + 1

NOTE: There are 10 values in set A and there are 10 values in set B

When we subtract A - B, we can do so in PAIRS
A - B = (20 - 19) + (18 - 17) + (16 - 15) + . . . + (4 - 3) + (2 - 1)
= (1) + (1) + (1) + . . . + (1) + (1)
= 10 (since there are 10 PAIRS)

Answer: 10

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Brent
Brent Hanneson - Creator of GMATPrepNow.com
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