good ps

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good ps

by vaivish » Tue Aug 12, 2008 11:58 am
If S is the sum of the reciprocal of a list of consecutive integers from 201 to 300, inclusive, which of the following about S is true?
(A) 0<S<1/3
(B) 1/4<S<1/3
(C) 1/3 < S < 1/2
(D) 1/2<S<2/3
(E) 2/3<S<1


OA is C
Source: — Problem Solving |

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by lachlanc » Tue Aug 12, 2008 12:53 pm
I'm going with (C)

Take the average reciprocal of 1/250 and multiply it by 100, you should get 10/25 or 0.4

Is that correct?

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by malolakrupa » Thu Aug 14, 2008 12:33 pm
Are the answer options correct , because the sum would be 1/201 + 1/202 ....1/300 , so the mimimum value is approxilately 0.005 and the last value is 0.0033 and I am not able to relate this to any of the answers.

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by anju » Thu Aug 14, 2008 12:37 pm
GMAT gurus pls. explain this

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Re: good ps

by Stuart@KaplanGMAT » Thu Aug 14, 2008 1:39 pm
vaivish wrote:If S is the sum of the reciprocal of a list of consecutive integers from 201 to 300, inclusive, which of the following about S is true?
(A) 0<S<1/3
(B) 1/4<S<1/3
(C) 1/3 < S < 1/2
(D) 1/2<S<2/3
(E) 2/3<S<1


OA is C
We have 100 numbers on our list and we REALLY don't want to add them up. However, the answers are pretty big ranges (relative to our numbers, anyway), so let's look at the 2 extreme cases.

If every number had been 1/200, then the sum would be 100/200 = 1/2.

if every number had been 1/300, then the sum would be 100/300 = 1/3.

Our sum will be between the two extremes: choose (c), 1/3 < S < 1/2.
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