Question 638269
John drives a car from Statesville NC to Wilmington NC.  During the first part of the trip he drove at a rate of 60 mph, but later traffic was very heavy and in the second part of the trip he could only drive at a rat of 40 mph.  If it is 240 miles from Statesville to Wilmington and if the whole trip takes 5 hours, how far does John drive at 40 mph and how far does he drive at 60 mph?

I really want to understand exactly how to do this.  If you could please break it down simple so I can understand it and be able to "click" in my brain.

Thank you!


Let the distance that John drove at 40 mph be D


Then distance he drove at 60 mph = 240 - D


Time taken to drive at 40 mph, plus time taken to drive at 60 mph, equals total time, 


OR


{{{D/40 + (240 - D)/60 = 5}}}

3D + 2(240 – D) = 600 ------ Multiplying by LCD, 120
3D + 480 – 2D = 600
3D – 2D = 600 – 480
D, or distance driven at 40 mph = {{{highlight_green(120)}}} miles

Distance driven at 60 mph = 240 – 120, or {{{highlight_green(120)}}} miles


You can do the check!!


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