The big ideaKeep the total so far on the frame, and add the next number on top.
How it works
Adding a column is just adding one number at a time.
Keep the total so far on the frame, and add the next number on top. The frame remembers it for you.
Hunt for friendly pairs first: two numbers that make ten, like 6 and 4 or 8 and 2, are easy.
Written down or on the frame, a carry works the same way.
Adding a column on the frame.
Example 1: Two numbers first
Set 26 on the frame. Add 38 on top.
Ones: 6 + 8 = 14, so carry a ten and keep 4.
Tens: 2 + 3 + 1 = 6.
26 + 38 = 64
The total so far is 64.
Example 2: Add the third on top
The frame still shows 64. Add 19 on top.
Ones: 4 + 9 = 13, so carry a ten and keep 3.
Tens: 6 + 1 + 1 = 8.
64 + 19 = 83
The total is 83.
Example 3: A different order
Add the same numbers as 19, then 26, then 38.
19 + 26 = 45
45 + 38 = 83
The carries come in different places, but the total is the same.
Example 4: Four numbers
36 + 45 + 28 + 14 passes one hundred, so use three rows.
36 + 45 = 81
81 + 28 = 109
109 + 14 = 123
The total is 123.
Words to know
column
Numbers written one under the other, added one at a time.
total so far
What the frame shows after each number you have added.
friendly pair
Two numbers that make ten, like 6 and 4.
carry
The ten that moves up a row when a row is full.
Watch out
Say the total so far out loud after each number, so you never lose your place.
Check the carry at every step, not just the last one.
A running total can pass one hundred. Then you need the third row.
Try it
What is 35 + 28 + 17?
What is 46 + 27 + 18?
What is 24 + 31 + 12?
What is the friendly partner of 6, the number that makes ten with it?
Answers: 1. 80 · 2. 91 · 3. 67 · 4. 4
Try at homeAsk a grown-up for three or four prices from a shop leaflet. Add the first two, say the total so far, then add the next one on top. Then add them again in a different order and see if the total is the same.
For grown-upsTake three or four prices from a shop leaflet. Add them in one order, then again in a different order, and see that the total is the same.
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