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 = 
<gadget id="calculator">6/60</gadget>
<output>1/10 = around 0.1</output>
.1.
While the album is playing he can run 4 miles because 40 x .1 = 
<gadget id="calculator">40*.1</gadget>
<output>4</output>
4.
He has to run 2 miles without the album because 6 - 4 = 
<gadget id="calculator">6-4</gadget>
<output>2</output>
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) = 
<gadget id="calculator">2/(1/15)</gadget>
<output>30</output>
30.
It will take him 70 minutes in total because 40 + 30 =
<gadget id="calculator">40+30</gadget>
<output>70</output>
70.

<result>70</result>