Number system

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Number system

by vipulgoyal » Mon Apr 22, 2013 3:33 am
15) 0<=n<=9, what is the value of n
1). if tenth unit of 1/n is zero
2). if unit digit of 1/n >=n

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by Anju@Gurome » Mon Apr 22, 2013 4:22 am
Another poorly constructed problem.
  • 1. The statements of a proper data sufficiency problem would never be like "If something is true..."
    2. The term 'tenth unit of 1/n is zero' doesn't make any sense.
    3. From question stem, a possible value of n is 0. But the statements are talking about 1/n which is undefined for n = 0. GMAT would never allow this situation to arise at all.
A proper data sufficiency problem would be...
vipulgoyal wrote:15) If 0 < n ≤ 9, what is the value of n?

1) Tenths digit of 1/n is zero
2) Units digit of 1/n ≥ n
Statement 1: If n = 1, tenths digit of 1/n = 1.0 is zero.
If n = any other value, 1/n will have a non-zero tenths digit. This can be proved by checking the tenths digit of 1/9 as 1/9 is the smallest possible value of 1/n. 1/9 = 0.11...

So, only possible value of n is 1.

Sufficient

Statement 2: If n = 1, units digit of 1/n = 1.0 is 1 and 1 ≥ 1
If n = any other value, the units digit of 1/n will be always zero, as 1/n will be fraction less than 1. Hence, the units digit of 1/n will be less than n.

So, only possible value of n is 1.

Sufficient

The correct answer is D.
Anju Agarwal
Quant Expert, Gurome

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