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GMAT Prep?? (Sum of even)

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by VP_Jim » Thu May 15, 2008 9:19 pm
Hi dferm,

There's a really quick way to solve these. Note that the average of all the even numbers between 100 and 200 is going to be about 150. Then, note that we have about 50 even numbers between 100 and 200.

So, if we take 150 * 50, we get 7500, which is close to the right answer (close enough!).
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by sandeep_chhabra » Thu May 15, 2008 9:51 pm
AP can be easily used:

n/2 [2a + (n-1)d]

n=Total even numbers between 102 & 200 = 50
a=first term =102
d=2

=>25 [204+(49)2]
=>25[302]
=>7550
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by bia » Thu May 15, 2008 9:56 pm
We got the formula to get the sum of even integers:

S = (a1 + an)x(number of integers)/2

Apply to this question :
a1=102; an=200
number of integers = ((200-102)/2) + 1 = 50

S= (102+200)x50/2 = 7550
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