Add back what you took away. If you land on the start, it is right.
Adding and taking away undo each other, like putting four blocks on and taking four off.
After a take away, add back what you took away. If you land on the start, your answer is right.
It works the other way too: to check an add, take a part away, and you land on the other part.
A check takes only a moment, and it catches a slip before it grows.
These are some of the questions on the sets. The printable sheets have more, with the bead frame drawn for each, and an answer key.
91. 91 is the start, so 55 is right.
81. 81 is not 75, so Ben's answer is wrong.
37. Open a ten: 6 tens and 15 ones. 15 - 8 = 7 and 6 - 3 = 3. Check: 37 + 38 lands on 75.
34 + 38. Add back what you took away: 34 and 38 should make 72.
Ask a grown-up to give you a take away sum, like the number of pages in a book you are reading. Work it out, then add the part you took away back on. Did you land on the start? If not, hunt for the slip together.
Give your child a take away sum from real life, such as pages left in a book. Work it out, then add the part back and check you land on the start.
