Reviewed by an experienced teacher. Not yet classroom-trialled.
PUPIL · 1
Regroup without changing the number
Skill: combine or exchange groups of ten while keeping the same total.
3 thousands, 3 hundreds, 12 tens and 2 ones
Ten of the twelve tens make one more hundred.
Each small square is 1. A rod is 10. A hundred grid is 100.
| Groups | Thousands | Hundreds | Tens | Ones |
|---|
| Before | 3 | 3 | 12 | 2 |
| After | 3 | 4 | 2 | 2 |
Keep the 3 thousands and the 2 ones. Combine the new hundred with the 3 hundreds.
3000 + 300 + 120 + 2
= 3000 + 400 + 20 + 2
= 3422
= means the same amount. The groups change; the number does not.
PUPIL · 2
Work in both directions
An exchange can make more groups of a smaller unit, or fewer groups of a larger unit.
Break one hundred into ten tens
430 = 4 hundreds + 3 tens
= 3 hundreds + 13 tens
400 + 30 = 300 + 130. Remove one hundred when you add ten tens.
Keep the ones
352 = 2 hundreds + 15 tens + 2 ones
200 + 150 + 2 = 352. The 2 ones have not changed.
A place can become empty
5300 = 5 thousands + 2 hundreds
+ 10 tens + 0 ones
Combine the 10 tens into a hundred again:
5000 + 200 + 100 = 5300
The tens and ones digits are zero in 5300.
PUPIL · 3
Your turn
Name: ____________________ Date: __________
Show your thinking with groups, words or a sum.
A
2 hundreds, 14 tens and 3 ones. Write the number.
B
2 thousands, 4 hundreds, 16 tens and 5 ones. Write the number.
C
470 = 3 hundreds + ____ tens. Explain the exchange.
D
6218 = 6 thousands + 1 hundred + ____ tens + 8 ones.
E
5 thousands, no hundreds, 13 tens and no ones. Write the number.
F
Sam says 2 thousands, 5 hundreds, 14 tens and 6 ones is 2546. Is Sam right? Explain.