How many elements are in the intersection of the set of all the prime numbers less than 30 and the set of all the odd numbers greater than zero?
I know that a prime number is a positive integer that has exactly two factors, one and itself. I also know that an odd number is an integer that is not divisible by two. To find the intersection of two sets, I need to look for the elements that are common to both sets. I can list out the elements of each set and then compare them. The set of all the prime numbers less than 30 is {2, 3, 5, 7, 11, 13, 17, 19, 23, 29}. The set of all the odd numbers greater than zero is {1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, ...}. I can see that the common elements are {3, 5, 7, 11, 13, 17, 19, 23, 29}. There are nine elements in this set, so the intersection has nine elements. 