Math
posted by Sahana on .
Hi. I found this question on a Math Counts practice test and it seriously confused me. I've never learned about this, and it would help if someone helped me. Thanks in advance.
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?
Problems
1. I don't even understand the question.
2. What does the question mean by elements?
3. Pleas don't just give me the answer, because I really want to know how to solve these types of questions in case it appears later on.

First, brush up the notion of sets. For example:
http://en.wikipedia.org/wiki/Set_%28mathematics%29
The intersection of two sets A and B is written as:
A∩B
Set A could be defined as :{1,2,3,4,5}
and set B could be defined as:{2,4,6,8,10)
The intersection of sets A and B, A∩B, is another set containing members which are present in both A and B, namely A∩B={2,4}.
So whis is the intersection of the set of primes less than 30,
P={2,3,5,7,11,13,17,19,23,29}
and the set of all positive odd numbers,
Q={1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,....ad infinitum}
So what is P∩Q?
Post what you think.