Counting on and back to 20 Learn on how to count on and back from 0 to 20. Comparing numbers within 20 Find out how to compare numbers 1 - 20, using number lines and symbols. Odd and even numbers ...

you start at 20 and count back until you reach 1 (or zero). Each number is one less than the last. You can use number lines like the one below to help you learn how to count on and count back.