Count On Strategy

Our Big Idea in math right now is "Representing numbers in different ways helps combine and take away numbers." We are asking ourselves "How can we use facts we already know to solve other math problems?"  We have been learning about turn around facts, fact families, and count on facts for both single and double digit numbers.  For example we know 7+3=10 by counting on 3 from 7.  So we also know the turn around 3+7=10. Since we know the parts 7 and 3 make the total 10, we also know the rest of the fact family 10-7=3 and 10-3=7.  We can extend the count on strategy to double digit numbers.  For example we know 2+5=7, so we know 20+50=70 and 21+50=71.