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OG 172 - help?

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OG 172 - help?

by cpay3245 » Mon Apr 22, 2013 3:11 am
For any positive integer n, the sum of the first N positive integers equals n(n+1)/2.

What is the sum of all the even integers between 99 and 301?

10100
20200
22650
40200
45150
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by Anju@Gurome » Mon Apr 22, 2013 3:35 am
It is easier to solve this problem without using the given formula.
Number of even integers between 99 and 301 = (301 - 99)/2 = 202/2 = 101
Now, average of these even integers = (first integer + last integer)/2 = (100 + 300)/2 = 400/2 = 200

Hence, sum of the integers = 101*200 = 20,200

The correct answer is C.

Have a look at this post >> https://www.beatthegmat.com/og13-q172-ps ... tml#624461
A number of different methods for solving this problem has been discussed there.
Anju Agarwal
Quant Expert, Gurome

Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.

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