1990 AHSME Problems/Problem 11

Problem

How many positive integers less than $50$ have an odd number of positive integer divisors?

$\text{(A) } 3\quad \text{(B) } 5\quad \text{(C) } 7\quad \text{(D) } 9\quad \text{(E) } 11$

Divisors come in pairs, unless there is an integer square root, so we just need the perfect squares below $50$ . There are $7$ , so $\fbox{C}$

1990 AHSME (Problems • Answer Key • Resources)
Preceded by Problem 10	Followed by Problem 12
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