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Abacus · Ages 7+ · Set A
Multiplying two digits
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Goal: 15 min
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Remember: Split the second number into tens and ones. Build the ones part, keep the beads, then add the tens part.

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Chairs for the playThe school play was that night, and Mia and Ben were setting out chairs. There were twelve rows with sixteen chairs in every row. Counting every chair would take all night, so Pip showed them a faster way. Twelve rows is ten rows and two rows. First they did ten rows of sixteen: times ten moves every bead up one row. Then they did the two rows that were left. At the end they joined the two parts. Hundreds stay hundreds, tens add to tens, and ones add to ones.
1
Pip split twelve rows into which two parts?
twelve rows and two rowsten rows and two rowsten rows and ten rows
2
Ten rows of sixteen chairs: every bead moves up a row. That is chairs.
3
Which frame shows ten rows of sixteen, 160?
A
B
C
4
Now the two rows left: 2 × 16 =
5
Join the two parts: 160 + 32 =

Build it in parts

6
To find 12 × 23, you can find 10 × 23 and 2 × 23, then add the two parts.
TrueFalse
7
The frame shows 39, from 13 × 3. Keep the beads and add ten rows of 13, which is 130. Now it shows .
8
Join each rows-of-12 fact to its total.
  1. 110 × 12
  2. 22 × 12
  3. 311 × 12
  4. 412 × 12
  • A132
  • B24
  • C120
  • D144
9
Ben worked 12 × 15. He added 150 and 20 and got 170. What went wrong?
Ten rows of 15 should be 105He should have taken the parts awayTwo rows of 15 make 30, not 20
10
Ben multiplies a number by 13. Which split is easiest to build on the frame?
ten and threesix and sevenfive and eight
11
Put the plan in order.
  • Split the second number into tens and ones
  • Build the ones part on the frame
  • Add the tens part on top
  • Keep the beads on the frame
12
Stretch: build 21 × 14. Ten rows of 21 is 210 and four rows of 21 is 84. Together:
13
Draw the beads for 2 × 14 on the empty frame.
14
Write how you would build 15 × 12 in two parts.
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Answer key · Set A
Multiplying two digits
1ten rows and two rows Twelve is ten and two, so twelve rows is ten rows and two rows.
2160 Sixteen is 1 ten and 6 ones. Times ten moves each bead up a row: 1 hundred and 6 tens.
3C Each bead of 16 moved up a row: one bead on the hundreds row, six on the tens row, none on the ones.
432 2 × 6 is 12 ones: a ten trades up and 2 ones stay. 2 tens and the traded ten make 3 tens.
5192 Hundreds stay hundreds, tens add to tens, and ones add to ones: 1 hundred, 9 tens, 2 ones.
6True Twelve groups of 23 are ten groups and two groups. Add the parts: 230 + 46 = 276.
7169 Keep the beads and add the next part on top: 39 and 130 make 169.
81-C, 2-B, 3-A, 4-D
9Two rows of 15 make 30, not 20 2 × 15 is 30, so 150 + 30 = 180.
10ten and three Ten is just a move up a row, so ten and three is the easiest split.
111, 2, 4, 3 Do the ones part first and keep the beads, then add the tens part.
12294 Join the parts: 210 + 84 = 294. The hundreds, tens and ones add place by place.
14Your own words: a grown-up reads it.
Mark each answer, count the right ones and write the score on the sheet.