Kelsey commute is 15 minutes longer than Christina's. If Christine drives 12 minutes for every 17 minutes Kelsey drives, how long is each commute?

Question

Kelsey commute is 15 minutes longer than Christina's. If Christine drives 12 minutes for every 17 minutes Kelsey drives, how long is each commute?

 

Answer 1

So you know that Christine drives 12 minutes for every 17 minutes Kelsey drives.  Let's say Christine's commute time is C and Kelsey's commute time is K.  Since you know that Kelsey's commute is 15 minutes longer than Christine's, you can make an equation relating their commute times.

 

K = C + 15

 

You can also relate the first bit of info that Christine drives 12 minutes for every 17 minutes Kelsey drives:

 

C = (12/17) * K

 

You can substitute the second equation into the first and solve for K.  You will find that K = 51 minutes.  You can plug this into either equation to find that C = 36 minutes.