If S is the sum of reciprocals of a list of consecutive

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If S is the sum of reciprocals of a list of consecutive [#permalink]

16 May 2012, 09:35

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75% (01:34) correct

25% (00:44) wrong

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If S is the sum of reciprocals of a list of consecutive integers from 45 to 54, inclusive, S is approximately equal to

A. 0.1
B. 0.2
C. 0.3
D. 0.4
E. 0.5

Sorry, don't have an official answer.

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Re: If S is the sum of reciprocals of a list of consecutive [#permalink]

16 May 2012, 09:42

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gmihir wrote:

If S is the sum of reciprocals of a list of consecutive integers from 45 to 54, inclusive, S is approximately equal to

A. 0.1
B. 0.2
C. 0.3
D. 0.4
E. 0.5

Sorry, don't have an official answer.

We need to find the approximate value of 1/45+1/46+1/47+1/48+1/49+1/50+1/51+1/52+1/53+1/54. Now, the sum of these 10 terms will be very close to 10 times 1/50, which is 0.02*10=0.2.

Answer: B.
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Re: If S is the sum of reciprocals of a list of consecutive [#permalink]

24 Aug 2012, 04:27

Are these kind of progressions tested on the GMAT?

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Re: If S is the sum of reciprocals of a list of consecutive [#permalink]

24 Aug 2012, 10:09

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+1 B

All those numbers are close to 0.02.

Amogh: yes, that would be a GMAT question. You don't have to calculate, just estimate.
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Re: If S is the sum of reciprocals of a list of consecutive [#permalink]

05 Nov 2012, 15:18

I got 0.2 too (B). Please help. Here is my approach
(1/45) + (1/46) + .....+(1/54) = (45-44)/45 +(46-45)/46 +.....+(54-53)/54
= 10 -(44/45 + 45/46 + ...53/54). Each term in the bracket is > 0.977, and there are ten of them. Then their sum is roughly 9.8
10-9.8 = 0.2. But is this doable in 2 mn under stress and heat?
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Re: If S is the sum of reciprocals of a list of consecutive [#permalink]

06 Nov 2012, 13:47

my method was 1/45 + 1/46 + ... => 10/45 ~ 2/9 ~ .2

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Re: If S is the sum of reciprocals of a list of consecutive [#permalink]

19 Dec 2012, 03:59

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gmihir wrote:

If S is the sum of reciprocals of a list of consecutive integers from 45 to 54, inclusive, S is approximately equal to

A. 0.1
B. 0.2
C. 0.3
D. 0.4
E. 0.5

Sorry, don't have an official answer.

Solved this using Bunuel's technique that I saw on another similar problem.

S = \frac{1}{45}+\frac{1}{46}+...+\frac{1}{54}

Get number of terms: 54 - 45 + 1 = 10

Get lower limit: 10*\frac{1}{54}=\frac{5}{27}=0.18
Get upper limit: 10*\frac{1}{45}=\frac{2}{9}=0.22

0.18<S<0.22

Answer: B

Re: If S is the sum of reciprocals of a list of consecutive [#permalink] 19 Dec 2012, 03:59

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If S is the sum of reciprocals of a list of consecutive

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If S is the sum of reciprocals of a list of consecutive

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