UK Primary (3-6)
topic badge
Extending multiplication to larger numbers
Lesson

 

When we looked at the 10 times tables, we discussed how important place value is because each column in the place value table is $10$10 times larger than the previous one.

$10$10 units make a ten, $10$10 tens make a hundred, $10$10 hundreds make a thousand and so on.

Let's build on that knowledge and discuss how we can use it to multiply larger numbers.

 

 

 

What is $6\times7$6×7?

As we know our multiplication fact of $6\times7$6×7 is $42$42.

We can use this to answer questions like $6\times70$6×70, or $6\times700$6×700 or even $60\times70$60×70

Let's see how.

$6\times70$6×70

$6\times70$6×70 is the same as $6\times\left(7\times10\right)$6×(7×10) which we can write as $6\times7\times10$6×7×10

As multiplication is commutative, we can complete this multiplication in any order we like, so as we know $6\times7$6×7 is $42$42, then the final multiplication is by $10$10 which is a final easy step. 

$6\times7\times10=42\times10=420$6×7×10=42×10=420

 

$6\times700$6×700

The same process can be applied to $6\times700.$6×700.

Rewrite (or imagine) $6\times700$6×700 $=$= $6\times7\times100$6×7×100
Do the $6\times7$6×7 component   $=$= $42\times100$42×100
Then the multiplication of $100$100   $=$= $4200$4200

 

$60\times70$60×70

Rewrite (or imagine)  $60\times70$60×70 $=$= $6\times10\times7\times10$6×10×7×10
Regroup the multiplication by $10$10's   $=$= $6\times7\times100$6×7×100
Do the $6\times7$6×7 component   $=$= $42\times100$42×100
Complete the multiplication   $=$= $4200$4200

 

Worked Examples

Question 1

If $2\times8=16$2×8=16, what is $20\times8$20×8?

 

Question 2

Using your knowledge of place value, solve these related number facts.

  1. $3\times12$3×12=

  2. $30\times120$30×120=

 
Question 3

Using your knowledge of place value, solve these related number facts.

  1. $2\times18$2×18=

  2. $20\times18$20×18=

  3. $2\times180$2×180=

  4. $20\times180$20×180=

What is Mathspace

About Mathspace