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Homeschool math, Grade 5, multiplying multi-digit numbers

Why does my child forget the carried numbers in multiplication?

For example: 256 × 3 = 658

The right answer is 768. Your child wrote 658 because they wrote the ones digit of each product and dropped the carried numbers. Lots of kids do this. It's fixable, and you can start tonight. In LOOP we call it "Dropped the carries."

Your child isn't being careless. The facts are fine. They skip the step where the extra ten gets passed to the next column.

What they wrote256× 3658
The right answer256× 3768
Here is what happened. 6 × 3 = 18, and they wrote 8 but never carried the 1. Then 5 × 3 = 15, and they wrote 5 but never carried that 1 either. Then 2 × 3 = 6. Together that reads 658.

Here is the right way. 6 × 3 = 18: write 8, carry 1. 5 × 3 = 15, and 15 + 1 = 16: write 6, carry 1. 2 × 3 = 6, and 6 + 1 = 7. The answer is 768.

Is it this, or something else?

Before you fix anything, look at what they actually wrote.

658Dropped the carries. This is the page you're on.
988Added the carry before multiplying. They did (5 + 1) × 3 instead of 5 × 3 + 1.
758Their method is fine; one fact slipped. Check which fact: 5 × 3 is the usual one (14 instead of 15).

One wrong answer might just be a slip. If the same thing shows up again and again, it isn't. The sheet below will show you whether this is a pattern.

Free printable: 12 problems

Two of these (143 × 2 and 312 × 3) need no carrying, so they are your check. If those two come back right and the other ten are all wrong, this is probably the mistake. Check the key below for the exact wrong answers.

It prints on its own page.

Answer key

1. 768, 2. 948, 3. 945, 4. 286, 5. 774, 6. 738, 7. 688, 8. 668, 9. 936, 10. 645, 11. 822, 12. 740.

A child making this mistake will write 658, 608, 715, 664, 628, 488, 448, 505, 612, 420 for problems 1, 2, 3, 5, 6, 7, 8, 10, 11 and 12. Every one is smaller than the true answer. Problems 4 and 9 stay correct.

Multiplying with carrying
Name ____________Date ________Multiply. Use a pencil.
1.256× 3
2.158× 6
3.135× 7
4.143× 2
5.387× 2
6.246× 3
7.172× 4
8.167× 4
9.312× 3
10.129× 5
11.274× 3
12.185× 4
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What to do this week

  1. Day 1: Use 256 × 3 with blocks or coins: 2 hundreds, 5 tens and 6 ones, three times over. Have your child put all the ones together. They have 18 ones. Pause there, and don't tell them the trade. If they get stuck, ask what 10 ones can turn into. Once they trade 10 ones for a ten, the tens column has one more, and the carry makes sense.
  2. Day 2: Same problems, now on paper. Before each column, have them say out loud: "Did the last column make a ten or more?" In 256 × 3, 6 × 3 is 18, so yes, write 8 and carry the 1 above the 5.
  3. Day 3: Do the printable again and count how many are still too small. If most of the ten are right now, you're good. If they're still getting the same wrong answer, do Day 1 again.

LOOP does this for every page. Your child does a printed page in pencil. You take a photo. LOOP tells you which mistake showed up on each problem and prints the next page. Your child works on paper the whole time.

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Tyler Judson, LOOP co-founder. Before LOOP I tutored math, one kid at a time. LOOP is my try at giving every kid that kind of attention without a tutor in the room.

The mistake names are the ones LOOP uses for Grade 5 multiplication. The examples were checked by running LOOP's mistake-finder.

Know what your child is missing, on paper.

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