M3.2.3 For the adult
Long multiplication
How do I work out 346 × 52 on paper?
What this chapter teaches
Long multiplication multiplies by each digit of the second number and adds the rows. The row for the tens starts with a zero because that digit is worth ten times as much. The grid method shows the same calculation as boxes.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why is the second row of 346 × 52 worth 346 × 50?
- What does the 0 at the start of row 2 hold?
- How could you check that 17 992 is about the right size?
After the chapter, the learner can
- Multiply a 3 digit number by a 2 digit number
- Explain why the second row starts with a zero
What they copy into their notebook
Multiply by the ones. Then write a 0 and multiply by the tens. Add the two rows. The 0 is there because the second row is worth tens.