Needgmat wrote:If n is a positive integer, what is the ten digit of n?

1) The hundreds digit of 10n is 6

2) The tens digit of n+1 is 7

Statement 1:
10n = 600, 610, 620, 630...

If we divide both sides by 10, we get the following options for n:
n = 60, 61, 62, 63...
In every case, the tens digit of n is 6.
SUFFICIENT.

Statement 2:
n+1 = 70, 71, 72...

If we subtract 1 from both sides, we get the following options for n:
n = 69, 70, 71...

If n=69, then its tens digit is 6.
If n=70, then its tens digit is 7.
Since the tens digit can be different values, INSUFFICIENT.

The correct answer is A.

Hello Mitch Hunt and other experts......

I understood your explanations. Please help me in my below logic where I go wrong..

Statement 1. hundreds digit of 10n is 6...So, let n=61-> so 10n=610.. hundred digit is 6 but ten digit is 1.

let n=62-> .. hundred digit of 10n=620 but ten digit of n is 2.. So INSUFFICIENT.

Statement 2.The tens digit of n+1 is 7. If n is a 2 digit positive integer (to get tens digit atleast) n has to be 69, to get 69+1=70.. so 69...let n=169 so n+1=170.. so still tens digit is 7, but n is 169.. Hence in sufficient..

Both together will say that only with number n=69, 10n=690.. so Statement 1 sufficient and 69+1=70.. So Statement 2 sufficient...

So OA shoudl be C.

Please explain where I go wrong in above explanation.

Regards,

Mrudang

mjmehta81 wrote: Statement 1. hundreds digit of 10n is 6...So, let n=61-> so 10n=610.. hundred digit is 6 but ten digit is 1.

let n=62-> .. hundred digit of 10n=620 but ten digit of n is 2.. So INSUFFICIENT.

This is a totally reasonable and common objection, but remember that you don't have to tell us *everything* about n: you only have to give us what the question seeks. Since we're only asked for the tens digit of n, the units digit of n (the tens digit of 10n) is irrelevant.

It's nice to be complete and thorough, but that instinct can get us in real trouble in DS.