Question

My daughter brought home this question:
How does knowing 28=30-2 help you find 13+28?
Any ideas?
Amanda
Because then you can figure out what 11 more than 30 is. That is easier than trying to add 13 and 28 in your head.
bobpursley
Yes, it is a matter of grouping:

13+ 28= (11+2)+28= 11 + (2+28)= 11+30
justin
length in feet and inches