IMO Abeater wrote:If the units digit of the three-digit positive integer k is nonzero, what is the tens digit of k?
(1) The tens digit of k + 9 is 3.
(2) The tens digit of k + 4 is 2.
statement (1)
let k = xyz [3 digit, unit digit non zero]
x y z
++9
____
x30
minimum value of z can be 1 since it is non zero integer.
1+9 = 10
1 carry over to the tens y+1 = 3 , y =2
maximum value of z can be 9
9+9 = 18
1 carry over to the tens y+1 = 3 , y =2
Sufficient.
Statement (2)
x y z
++4
____
x2(z+4)
z=1, 1+4 = 5, y=2
z=9, 9+4 = 13, 1 carry over, if y=1, tens digit will be 2. Insufficient.
Thus, A.
OA?












