Racing car combos

This task is about finding all possible combinations.
Practical Task
At the start line of a race cars can be ordered in different ways.
For example: 2 cars could be ordered either:
 
or
1 2 2 1
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Cut out the pictures of the cars from the sheet and use them to help you solve the problems below.
 
a)
List all the different ways 3 cars could be ordered at the start line.
 
 
 
 
 
 
 
b)
List all the different ways 4 cars could be ordered at the start line.
 
 
 
 
 
 
 

Template sheet - cars

 

1

 
 

2

     
 

3

 

4