Use place value
6 x 4 = 24 helps us see that 60 x 4 = 240.
One factor is ten times larger, so the product is ten times larger.
Year 4
Use place value, known and derived facts to multiply and divide mentally
Use known table facts, doubling, halving and place value to work out related multiplication and division facts mentally.
Lesson overview
Number - multiplication and division
Derived facts come from facts we already know. If 6 x 4 = 24, then 60 x 4 = 240. If 12 x 3 = 36, then 36 ÷ 3 = 12. Place value and known facts help us reason quickly.
Use doubling
6 x 7 = 42, so 12 x 7 = 84.
Doubling one factor doubles the product.
Use inverse thinking
If 9 x 8 = 72, then 72 ÷ 9 = 8.
Multiplication facts help division facts.
Worked example
Use 7 x 6 = 42 to work out 70 x 6.
- Start with the known fact 7 x 6 = 42.
- 70 is ten times greater than 7.
- So the product must be ten times greater than 42.
- That makes 420.
Round 1: Learn it
Start from a fact you know, then decide whether to use place value, doubling or inverse thinking.
Finish this round to unlock Round 2: Show you know it.
Question 1
If 6 x 4 = 24, what is 60 x 4?
Question 2
If 7 x 8 = 56, what is 56 ÷ 7?
Question 3
If 9 x 3 = 27, what is 90 x 3?
Question 4
If 6 x 5 = 30, what is 12 x 5?
Question 5
Which answer is correct for 84 ÷ 12?
Common mistakes
Watch for these as you work through the lesson.
- Forgetting to change the product when a factor changes.
- Ignoring the zero in a place-value fact.
- Using a division fact that does not match the same numbers.
Related topics
These ideas connect closely to this lesson.
- Recall multiplication and division facts for multiplication tables up to 12 x 12.
- Multiply two-digit and three-digit numbers by a one-digit number using formal written layout.