If n = p^2 and p is a prime number greater than 5, what is the units digit of n^2 ?
A. 1
B. 3
C. 4
D. 7
E. 9
OA A
Source: Official Guide
A. 1
B. 3
C. 4
D. 7
E. 9
OA A
Source: Official Guide
Say p = 7, then n^2 = p^4 = 7^4 = 49^2; the units digit of 49^2 is 1. The correct answer is A. There is no need to check for other prime numbers such as 11, 13, 17, etc. since this is a PS question, the correct option must be true for p = 7. As in PS questions, only one option is correct, the correct answer is A.BTGmoderatorDC wrote:If n = p^2 and p is a prime number greater than 5, what is the units digit of n^2 ?
A. 1
B. 3
C. 4
D. 7
E. 9
OA A
Source: Official Guide
You may try with p = 11 => n^4 = 11^4; units digit is 1. Again, say p = 19 => n^4 = 19^4; units digit is 1.
The correct answer: A
Hope this helps!
-Jay
_________________
Manhattan Review GRE Prep
Locations: GMAT Classes San Francisco | GRE Prep Course DC | GRE Prep Houston | SAT Prep Classes NYC | and many more...
Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
