Do you know an enumeration for all integers?

Do you know a bijection from integers to odd integers?

Compose these two and you have an enumeration for odd integers.

Do you know the enumeration for pairs of natural numbers ?2. Find an enumeration of the set of all rational numbers that have a terminating decimal representation.

(E.g. 17=10 = 1:7 and 17=8 = 2:125 are in this set, but 17=9 = 1:88888 : : : is

not.)

I'm not sure how to do this one

Find the bijection between paris of natural numbers and terminating decimals.

Again, compose