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Abacus · Ages 7+ · Set A
A full row trades up
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Goal: 15 min
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Remember: A carry is ten in a full row trading for one bead on the next row up. Count the new bead too.

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The bead stallMia has 36 beads and Ben has 28 beads. They add them on the counting frame. Mia puts 36 on it: three tens and six ones. Ben slides 8 more ones across. The ones row only holds ten, so four beads have nowhere to go. Here is the clever part: a full ones row trades for one ten. Ten ones slide back and one bead slides up on the tens row. Four ones stay behind. Now count the tens: three tens, two tens and the new ten. That is six tens and four ones.
1
How many beads do Mia and Ben have in all?
2
What does a full ones row trade for?
one bead on the hundreds rowone bead on the tens rownothing
3
After the trade, the ones row has no beads left.
TrueFalse
4
Ben counted only five tens and forgot something. What was it?
the new ten from the tradethe onesthe hundreds

On the frame

Look at the ones row first.

5
Which frame shows 36 + 28 after the trade? The top row is tens.
A
B
C
6
The frame shows 29. Add 15. 29 + 15 =
7
57 + 26 =
8
Circle every sum that needs a carry.
23 + 4536 + 2748 + 3552 + 31
9
34 + 25 needs a carry.
TrueFalse

Fix it and stretch

10
Ben added 36 + 28 and said 54. What did he forget?
to add the onesto add the tensthe carried ten
11
The carry can hop twice. 76 + 29 =
12
When the tens row is full, ten tens trade for one
tenhundredone
13
Number the steps of a carry.
  • Slide the ten ones back
  • Count the tens, with the new one
  • Slide one bead up on the tens row
  • Slide beads until the ones row is full
14
Say in your own words what a carry is.
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Answer key · Set A
A full row trades up
164 6 ones and 8 ones make 14 ones: one ten and four ones. With 5 tens, that makes 6 tens and 4 ones.
2one bead on the tens row Ten ones slide back and one bead slides up on the tens row.
3False 14 ones is one ten and four ones, so four ones stay on the bottom row.
4the new ten from the trade The bead that moved up counts too: 3 tens, 2 tens and the new ten make 6 tens.
5C Six tens and four ones. Frame A forgot the new ten.
644 9 + 5 = 14, so trade ten ones for a ten and keep 4. Then 2 + 1 + 1 = 4 tens.
783 7 ones and 6 ones make 13: a ten goes up and 3 stay. 5 + 2 + 1 = 8 tens.
836 + 27, 48 + 35 6 + 7 = 13 and 8 + 5 = 13 fill the ones row. 3 + 5 and 2 + 1 do not.
9False 4 + 5 = 9, which fits in the ones row, so nothing needs to trade up.
10the carried ten The right answer is 64. Ben counted 3 tens and 2 tens but not the ten that moved up.
11105 6 + 9 = 15: carry a ten. 7 + 2 + 1 = 10 tens, and ten tens trade for one hundred. That is 105.
12hundred Ten tens make one hundred.
132, 4, 3, 1 Fill the row, trade it, then count the new ten with the others.
14Your own words: a grown-up reads it.
Mark each answer, count the right ones and write the score on the sheet.