best method to solve it

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by jaymw » Mon Apr 18, 2011 8:17 pm
This problem should be solved using estimation techniques.

Let us look at the denominator first.

1/0.07 is a little more than 14. To know why, ask yourself how many times 7 fits into 100. 14*7=98 so the first fraction will be a little greater than 14.

Same goes for the second fraction in the denominator. How many times does 16 fit into 100? 6 times! 6*16=96 so that fraction will equal a little more than 6.

Together the denominator will be a little greater than 20.

Since the numerator is a little less than 5 and is devided by something a little greater than 20, we should expect a result that is LESS than 1/4. Only option A fullfils this!

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by Anurag@Gurome » Mon Apr 18, 2011 8:23 pm
alltimeacheiver wrote:4.896/(1/0.07 + 1/0.16)
is approximately equal to:


.238
.262
.625
.649
6.25
1/0.07 = 100/7 and 1/0.16 = 100/16 = 25/4
100/7 + 25/4 = 14 + 6 = 20 (approximately), if actually divide the values then this value be more than 20
Therefore, 4.896/(1/0.07 +1/0.16) = 5/20 = 1/4 = 0.25(approximately)
So, the value of the expression will be less than 0.25 as the actual value of 100/7 + 25/4 will be more than 20.

The correct answer is A.
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by alltimeacheiver » Mon Apr 18, 2011 8:36 pm
thanks good approach. i saw this question in Mgmat tests but u were at best approach