Use Partitioning to Multiply a Two-digit Number by a One-digit Number

In this activity, we will be multiplying a two-digit number by a one-digit number.

 

To do this, we need to partition the two-digit number into its place value. 

 

So, let's try multiplying 22 by 7. 

 

The first step is to partition 22.

22 can be partitioned into 20 and 2.

 

The next step is to multiply the ones and tens by 7.

2 × 7 = 14

20 × 7 = 140

 

The final step is to add the products together.

140 + 14 = 154

 

So, 22 × 7 = 154

 

Let's try an example question together. 

 

Example

Work out the missing number:  

23 × 4 =         

 

 

Answer

We are trying to work out 23 lots of 4.

23 can be partitioned into 20 and 3.

 

So we work out 20 lots of 4 and then 3 lots of 4.

20 × 4 =  80 

3 × 4 =  12 

 

Now add the products together.  

80 + 12 =  92

 

So, 23 × 4 =  92

 

Now you've seen the method to use, it's your turn to try some questions.