Transcript

NARRATOR:

Suppose that all the vehicles are motorbikes. Draw a diagram-- you don't have to be an artist-- that shows these 21 motorbikes. Be sure to use a representation that will allow you to clearly distinguish between 2 and 4 wheels. How many wheels do you have? There were 21 motorbikes, each with 2 wheels. So in total, there are 42 wheels.

However, Paul said that there were 54 wheels in total. So you need to add an additional 12 wheels because 54 take away 42 is 12. To work out how many motorbikes and cars the dealership has from here, you could just start adding two wheels to each motorbike until you've counted up to the 12, or you could change a motorbike into a car to gain two additional wheels.

Since you know you need 12 more wheels to reach the required total, you need to change 6 motorbikes to cars because 12 divided by 2 is 6. You can now see, there are six cars and 15 motorbikes, giving a total of 21 vehicles. You can check that the total number of wheels adds up to 54.

Each car has four wheels, which makes 6 times 4 equals 24 wheels. Each motorbike has 2 wheels, which makes 15 times 2 equals 30 wheels. Together, that is 24 plus 30 equals 54 wheels. So the dealership has 15 motorbikes and 6 cars in stock.