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OG 12 DS #166

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OG 12 DS #166

by sudi760mba » Sat Jan 22, 2011 2:39 pm
If n is a positive integer is (1/10)^n < 0.01?

(1) n > 2

I can understand why (1) is sufficient

(2) (1/10)^(n-1) < 0.1

But for statement 2
If I plug in 1 for n then
(1/10) ^0 = (1/1) = 1 which is greater than .1

If I plug in 2 for n then
(1/10)^ 1 = (1/10) = .1 which is equal to .1

If I plug in 3 for n then
(1/10)^2 = (1/100) = .01 which is less then .1

wouldn't this be insufficent then?

Thanks!
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by Rahul@gurome » Sat Jan 22, 2011 3:13 pm
sudi760mba wrote:(2) (1/10)^(n-1) < 0.1

But for statement 2
If I plug in 1 for n then
(1/10) ^0 = (1/1) = 1 which is greater than .1

If I plug in 2 for n then
(1/10)^ 1 = (1/10) = .1 which is equal to .1

If I plug in 3 for n then
(1/10)^2 = (1/100) = .01 which is less then .1

wouldn't this be insufficent then?

Thanks!
The question is not asking you to find a suitable value for n such that it satisfies the given statements. For a DS question, you've to consider the statements as true condition and then you've to proceed. For example, here you cannot assume a value of n such that it violates the statements. Hence, for statement 2, you cannot assume n to be equal to 1 or 2 as that doesn't satisfies statement 2.

The ideal analysis should be,
  • (1/10)^(n-1) < 0.1
    => [(1/10)^n]*[(1/10)^(-1)] < 0.1
    => [(1/10)^n]*(10) < 0.1
    => (1/10)^n < (0.1)/10 = 0.01
Hence, statement 2 is sufficient.

The correct answer is D.
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