word problem using units rates with fractions

Question

A tire shop had to fill 3 1/2 tires with air. It took a small air compressor 3 3/5 seconds to fill them up. How long would it take to fill 3 tires?

Answer 1

Hi Christy!

 

This problem is a simple conversion.

 

Let's first figure out how long it would take the tire shop to fill up 1 tire by dividing 3 3/5 by 3.

3 3/5 = 18/5

18/5 / 3 = 18/5 * 1/3 = 18/15 = 6/5

 

So, it takes 6/5 seconds to fill 1 tire.

Now, multiply this by 3 1/2 to get the time to fill 3 1/2 tires.

3 1/2 = 7/2

6/5 * 7/2 = 42/10 = 21/5 seconds = 4 1/5 seconds

 

Hope that helps :)