Given: If d is a single-digit number greater than 1, what is the value of d ?
(1) d is a factor of the two digit number d3, where d is the tens digit and 3 is the units digit.
(1) d is a factor of the two digit number d9, where d is the tens digit and 9 is the units digit.
Solution:
d > 1 and a single digit number
That means 1 < d <=9
Option 1: d is a factor of the two digit number d3, where d is the tens digit and 3 is the units digit.
2-digit numbers in the form of d3 are 23, 33, 43, 53, 63, 73, 83, 93 (13 isn't possible as d > 1)
Now if d = 2, 2 is not a factor of 23
if d = 3, 3 is a factor of 33
if d = 4, 4 is not a factor of 43
if d = 5, 5 is not a factor of 53
if d = 6, 6 is not a factor of 63
if d = 7, 7 is not a factor of 73
if d = 8, 8 is not a factor of 83
if d = 9, 9 is not a factor of 93
We get only 1 possible value of d3 i.e. 33
so that d = 3
SUFFICIENT
Option 2: d is a factor of the two digit number d9, where d is the tens digit and 9 is the units digit.
2-digit numbers in the form of d9 are 29, 39, 49, 59, 69, 79, 89, 99 (19 isn't possible as d > 1)
Now if d = 2, 2 is not a factor of 29
if d = 3, 3 is a factor of 39
if d = 4, 4 is not a factor of 49
if d = 5, 5 is not a factor of 59
if d = 6, 6 is not a factor of 69
if d = 7, 7 is not a factor of 79
if d = 8, 8 is not a factor of 89
if d = 9, 9 is a factor of 99
We get 2 possible value of d9 i.e. 39 and 99
so that d = 3 or d = 9
INSUFFICIENT
Option A is the correct choice