Ben twice chooses a random integer between 1 and 50, inclusive (and he may choose the same integer both times). What is the probability that at least one of the numbers Ben chooses is a multiple of 3?

There are 16 numbers that are divisible by 3 from 1 to 50, so the probability is 16/50*16/50 = 64/625.

Nice try, but...

What you have found is the prob that he chooses a number divsiable by 3 both times.

Can you fix it?