It is easier to calculate how many integers are perfect squares and then subtract that number from 50.
1² = 1
2² = 4
3² = 9
4² = 16
5² = 25
6² = 36
7² = 49
There are 7 numbers that have perfect squares, so there are 50 - 7 = 43 that have irrational square roots.
Answer: 43
