SOLUTION: A dirt biker must circle a 12-mile track twice. His average speed must be 60 mph. On his first lap, he averaged 50 mph. How fast must he travel on his second lap in order to qualif

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: A dirt biker must circle a 12-mile track twice. His average speed must be 60 mph. On his first lap, he averaged 50 mph. How fast must he travel on his second lap in order to qualif      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


   



Question 1120554: A dirt biker must circle a 12-mile track twice. His average speed must be 60 mph. On his first lap, he averaged 50 mph. How fast must he travel on his second lap in order to qualify?
Answer by ikleyn(52814) About Me  (Show Source):
You can put this solution on YOUR website!
.
The time equation is 


12%2Fx + 12%2F50 = 24%2F60.


Solve for x, where x is the speed on the second lap.


12*50*60 + 12*60*x = 24*50*x


12*50*60  = 24*50*x - 12*60*x


x = %2812%2A50%2A60%29%2F%2824%2A50-12%2A60%29 = 75.


Answer.  The speed under the question is 75 mph.


Check.  12%2F50 + 12%2F75 = 12%2A%281%2F50+%2B+1%2F75%29 = 12%2A%286%2F300+%2B+4%2F300%29 = 12%2A%2810%2F300%29 = 12%2A1%2F30 = 24%2F60 of an hour = 24 minutes.


        ! Correct !