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by Bhupisuhag » Wed Jun 13, 2012 6:07 am
If K is the sum of the reciprocals of the consecutive integers from 43 to 48, inclusive, then K is
closest in value to which of the following ?

1) 1/12
2) 1/10
3) 1/8
4) 1/6
5) 1/4

Better way to do this ?
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Source: — Problem Solving |

by Brent@GMATPrepNow » Wed Jun 13, 2012 6:39 am
Bhupisuhag wrote:If K is the sum of the reciprocals of the consecutive integers from 43 to 48, inclusive, then K is
closest in value to which of the following ?

1) 1/12
2) 1/10
3) 1/8
4) 1/6
5) 1/4
We want the approximate sum of 1/43 + 1/44 + 1/45 + . . . + 1/48

Let's make the following observations about the upper and lower bounds:
Upper bounds: If all 6 fractions were 1/43, the sum would be (6)(1/43) = 6/43 ~ 6/42 = 1/7
Lower bounds: If all 6 fractions were 1/48, the sum would be (6)(1/48) = 6/48 = 1/8

From this we can conclude that 1/8 < K < 1/7

If K is between 1/8 and 1/7, then K must be closer to 1/8 than it is to 1/6

Answer = C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Bhupisuhag » Wed Jun 13, 2012 9:30 am
Great help...Thx for this detailed explanations
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