Primary 5 Foundation maths · Operations · About 12 minutes
Multiply and divide up to two digits by one digit without a calculator
Split the number by place value, multiply each part, then put the parts back together.
Start the interactive lesson →Open practice activity
What you will learn
- Multiply and divide up to two digits by one digit without a calculator
Models used: number sentences, stories, diagrams.
Before you start
A large group can be split into smaller groups
We have 4 rows of 23. Each row can be split into 20 and 3.
Each little square is one square unit. There are 23 squares across and 4 rows.
We have 4 rows of 23. Each row can be split into 20 and 3.
23 × 4
The complete bar is the whole. Each labelled section is one part of it.
Four rows of 20 make 80. We can count those as four groups of two tens.
20 × 4 = 80
4 rows run across the picture; each row contains 3 objects.
The four extra groups of 3 make 12.
3 × 4 = 12
4 rows of 3 = 4 × 3 = 12
The complete bar is the whole. Each labelled section is one part of it.
Join both parts. Splitting the rows did not change the number of objects.
23 × 4 = 80 + 12 = 92
What did the picture help us see?
Join both parts. Splitting the rows did not change the number of objects.
Worked example: A new example, together
Calculate 12 × 5.
12 rows of 5 = 12 × 5 = 60
12 rows run across the picture; each row contains 5 objects.
Split the number by place value, multiply each part, then put the parts back together.
Multiplying each part of a amount and joining the products preserves the total.
12 rows run across the picture; each row contains 5 objects.
Split 12 by place value: 10 + 2.
Calculate 12 × 5.
60
12 rows run across the picture; each row contains 5 objects.
10 × 5 = 50; 2 × 5 = 10.
12 rows of 5 = 12 × 5 = 60
12 rows run across the picture; each row contains 5 objects.
Join the products: 50 + 10 = 60.
12 rows of 5 = 12 × 5 = 60
12 rows run across the picture; each row contains 5 objects.
Check the result against the question we started with.
60 ÷ 5 = 12.
We found 60. Multiplying each part of a amount and joining the products preserves the total.
12 rows of 5 = 12 × 5 = 60
Common mistakes to discuss
- Forgetting to carry into the next place. Each place is multiplied, and anything over nine moves on. 570 × 3 is 1710: the 21 tens become 1 hundred and 1 ten.
Check your understanding
- Multiply and divide up to two digits by one digit without a calculator
- multiply a larger number place by place
- check the answer against the original quantities and units
Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.
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