The big ideaTen in a full row trade for one bead on the next row up.
How it works
A row holds only ten beads. When a ones row fills up, ten ones trade for one bead on the tens row.
Slide the ten ones back and slide one bead up on the tens row. That ten that moves up is called a carry.
A full tens row trades too: ten tens trade for one hundred, so a carry can hop twice.
Add the ones first, trade when a row is full, then count the carried ten with the tens.
A carry, step by step.
Example 1: One carry
Put 36 on the frame. Slide 8 ones across: 6 + 8 = 14.
The ones row holds ten, so ten ones trade for one ten and four ones stay.
Tens: 3 + 2 + 1 = 6, counting the carried ten.
36 + 28 = 64
6 tens and 4 ones is 64.
Example 2: Another carry
Put 47 on the frame. Slide 5 ones across: 7 + 5 = 12.
Trade ten ones for a ten. Two ones stay.
Tens: 4 + 2 + 1 = 7.
47 + 25 = 72
7 tens and 2 ones is 72.
Example 3: The carried ten counts
38 + 46: the ones make 8 + 6 = 14, so one ten carries up and four ones stay.
Count 3 + 4 = 7 tens and you forget the carried ten.
Count the carried ten too: 3 + 4 + 1 = 8 tens.
38 + 46 = 84
8 tens and 4 ones is 84.
Example 4: Carry twice
Put 57 on the frame. Slide 8 ones across: 7 + 8 = 15. Trade ten ones for a ten and keep 5 ones.
Tens: 5 + 4 + 1 = 10 tens. A full tens row trades for one hundred.
That leaves one hundred, no tens and five ones.
57 + 48 = 105
1 hundred, 0 tens and 5 ones is 105.
Words to know
carry
The ten that moves up a row when a row is full.
trade
Ten beads on one row become one bead on the next row up.
full row
A row with ten beads slid across.
hundred
Ten tens, one bead on the top row.
Watch out
Do not forget the new ten. Count it with the tens.
A row holds a digit: 14 ones is one ten and four ones, never 14 beads on the ones row.
A full tens row trades for a hundred, so check the tens row after a carry.
Try it
What is 29 + 15?
What is 57 + 26?
What is 76 + 29?
What is 65 + 37?
Answers: 1. 44 · 2. 83 · 3. 105 · 4. 102
Try at homeAsk a grown-up for a pile of buttons or coins and a jar. Count out ten and swap them for one big button or one coin. Do it again until the pile is gone, and say how many swaps you made and how many were left over.
For grown-upsAt home, trade ten small things (buttons, coins) for one big thing, so your child feels what a carry is.
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