determine whether each of these sets is countable or uncountable. For those that are countable, exhibit a one to one correspondence between the set of natural nmbers and that set.
1. the odd negative integers
2. the real numbers between 0 and 2
3. integers that are multiples of 10
What does it mean for a set to be countably infinite (your second sentence is more or less a definition which should allow you to do 1 and 3 without much thought)
Question 2 should be just like at least one example that will have been covered in your lectures.