# Finite, countably infinite, or uncountable

• Mar 23rd 2011, 04:24 PM
JohnM25
Finite, countably infinite, or uncountable
Determine, with justification, whether each of the following sets is finite, countably infinite, or uncountable.

a) { $x \in Q | 1 < x < 2$ }

b) { $m/n | m, n \in N, m < 100, 5 < n < 105$ }

I am lost. Not sure how to approach these problems!

Thanks.
• Mar 23rd 2011, 04:37 PM
Plato
Quote:

Originally Posted by JohnM25
Determine, with justification, whether each of the following sets is finite, countably infinite, or uncountable.
a) { $x \in Q | 1 < x < 2$ }

b) { $m/n | m, n \in N, m < 100, 5 < n < 105$ }

For part a) A subset of a countable set is countable. Is it infinite?