Why does adding 2 odd numbers give an even number?
An even number can be divided by 2. If you try to divide an odd number by 2, there is always one left over.
If you take two odd numbers and divide them both by 2, there will be one left over for each number. By adding the two odd numbers together first, you pair up the left overs so there are two of them, which can be divided by 2.
(It is much harder writing this down than explaining in the pub...hopefully I'll get better at this!)
