Walkabout wrote:
If n is a positive integer, what is the tens digit of n ?
(1) The hundreds digit of 10n is 6.
(2) The tens digit of n + 1 is 7.
Target question: What is the tens digit of n? Statement 1: The hundreds digit of 10n is 6 Notice what happens when we multiply any positive integer by 10:
34 x 10 =
340
60 x 10 =
600
1
28 x 10 = 1
280
546
29 x 10 = 546
290
The tens digit in the original number becomes the hundreds digit in the new number.
So, if we're told that the hundreds digit of 10n is 6, then we know that
the tens digit in n must be 6Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: The tens digit of n+1 is 7 There are several values of n that meet this condition. Here are two:
case a: n=69 in which case
the tens digit of n is 6 case b: n=74 in which case
the tens digit of n is 7 Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT
Answer = A
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