Estimating and regrouping sums
Answers are for parents and teachers.
1
Estimate with the tens digits, then add exactly: 32 + 45, 51 + 36, 24 + 23.
Estimates 70, 80, 40. Real sums 77, 87, 47. Each real sum is close to its guess.
2
Use 10 beans for ones. Put 8 beans, then add 7 more. Trade 10 loose beans for a ten. What do you have?
15 beans: 1 ten and 5 ones.
3
Add with regrouping: 29 + 34, 45 + 38, 17 + 26.
63, 83 and 43.
4
Add the four numbers in pairs: 13 + 27 + 24 + 16.
13 + 27 = 40, 24 + 16 = 40. Total 80.
5
Ask someone at home for four numbers under 40. Add them in pairs and tell what you did.
Any correct total. The child pairs the numbers, adds each pair, then adds the two totals.