number now ends in zero and will be quite easy to square now.
secondly, add together 30 and 31 -- the number we squared plus the number we want to square.
add this to our sub-total, 900, to get 961 (900 + 61) , which becomes the answer.
note: for the second step you can simply double the number we squared, 30 x 2 and then add 1. 