vipulgoyal wrote:Which of the following cannot be a perfect square number?
A. 622,521
B. 99,856
C. 744,769
D. 426,408
E. 322,624
d
Aside: The GMAT will not assume that we know the meaning of "perfect square number." The phrase used it typically "square of an integer."
To answer the question we need only examine the units digit of the answer choices. Before we do that, however, we should make the following observations:
0² =
0
1² =
1
2² =
4
3² =
9
4² = 1
6
5² = 2
5
6² = 3
6
7² = 4
9
8² = 6
4
9² = 8
1
As we can see, any integer squared will have units digit
0, 1, 4, 5, 6 or 9
Answer:
D,, since it has units digit
8, and
8 cannot be the units digit of the square of an integer.
Cheers,
Brent
