Partition the number
23 x 4 can be seen as 20 x 4 and 3 x 4.
Split the two-digit number into tens and ones first.
Year 3
Multiply two-digit and one-digit numbers using practical resources and formal written layout
Use partitioning, arrays and an early written layout to multiply a two-digit number by a one-digit number.
Lesson overview
Number - multiplication and division
A two-digit number can be split into tens and ones. We can multiply each part and then combine the answers. Arrays and equal groups help us see why the method works.
Multiply each part
20 x 4 = 80 and 3 x 4 = 12.
Then combine the two partial products.
Combine the parts
80 + 12 = 92, so 23 x 4 = 92.
The final answer joins the tens part and the ones part.
Worked example
Work out 14 x 3.
3 rows of 14 split into 10 and 4
- Partition 14 into 10 and 4.
- Multiply 10 x 3 = 30.
- Multiply 4 x 3 = 12.
- Add 30 and 12 to get 42.
Try it
Split the two-digit number first, then multiply each part by the one-digit number.
Question 1
Which partition is correct for 16 x 4?
Question 2
What is 12 x 3?
Question 3
Work out 21 x 4.
Question 4
Which answer is correct for 13 x 4?
Question 5
Why do we partition 23 in 23 x 4?
Common mistakes
Watch for these when working through the lesson.
- Multiplying only the ones part and forgetting the tens part.
- Adding the original numbers instead of the partial products.
- Partitioning the number incorrectly.
Related topics
These ideas fit closely with this lesson.
- Mentally calculate using place value, known and derived facts.
- Solve problems, including missing number problems, involving multiplication and division.