A perfect square is a whole number whose square root is also a whole number. For example, 144 is a perfect square since its square root is 12 . How many perfect squares are there between 2 and 20 ?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
The whole numbers between 2 and 20 whose square root is a whole number are: 4,9,16 (since $\sqrt{4}=2, \sqrt{9}=3, \sqrt{16}=4)$.

We may note that perfect squares are equal to the square of an integer.

That is, the smallest five positive perfect squares are $1^{2}=1,2^{2}=4,3^{2}=9,4^{2}=16$ and $5^{2}=25$.

Of these five, there are three that are between 2 and 20 .

ANSWER: (D)

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