Charles is jogging while listening to his favorite album. He runs at 6 MPH when he's got music on and 4 MPH when he doesn't. His album is 40 minutes long. How many minutes will it take him to jog 6 miles?
He runs at .1 miles per minute because 6 / 60 = <<6/60=.1>>.1
While the album is playing he can run 4 miles because 40 x .1 = <<40*.1=4>>4
He has to run 2 miles without the album because 6 - 4 = <<6-4=2>>2
Without music he runs 1/15 miles per minute because 4 / 60 = 1/15
He will run the remaining 2 miles in 30 minutes because 2 / (1/15) = <<2/(1/15)=30>>30
It will take him 70 minutes in total because 40 + 30 =<<40+30=70>>70
#### 70