If a 20-sided fair die with sides distinctly numbered 1 through 20 is rolled, the probability that the answer is a perfect square can be expressed as a/b where a and b are coprime positive integers. What is the value of a+b?

Question

Reiny · Answer

the only squares from 1 to 20 are 1 , 4, 9, 16, that would be 4 of them So the prob(square) = 4/20 = 1/5 if 1/5 = a/b , in lowest terms, then a+b = 1+5 = 6

Steve · Answer

4 perfect squares out of 20 possibilities 4/20 = 1/5, so 1+5 = 6

Anonymous · Answer

A fair icosahedral die(number 1-20) is rolled. What is the probability that it will show: a factor of 20 or a prime number?