+4 a is chosen from the set {1,2,3,4}, and b is chosen from the set {5,6,7,8,9}. What is the probability that the product ab is a prime number?
+36916 Looks like 4 x 5 = 20 possibilities
only primes would be the primes in set 2 x one ===== 5 0r 7
2 out of 20 = 1/10 = .1 or 10%
