VJesus12 wrote:What is the units digit of 36^y?
(1) y is a positive integer
(2) y is an even integer
Target question: What is the units digit of 36^y?
Statement 1: y is a positive integer
So, y = 1 or 2 or 3 or 4 or 5 or...
Notice that 36^1 = 36 (units digit = 6)
Notice that 36^2 = ---6 (units digit = 6)
Notice that 36^3 = ---6 (units digit = 6)
Notice that 36^4 = ---6 (units digit = 6)
.
.
.
etc.
As we can see, if y is a positive integer,
the units digit of 36^y MUST be 6
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: y is an even integer
There are several values of y that satisfy statement 2. Here are two:
Case a: y = 0, in which case 36^y = 36^0 = 1. In this case,
the units digit is 1
Case b: y = 2, in which case 36^y = 36^2 = ---6. In this case,
the units digit is 6
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent
