SOLUTION: Hi Henry and Harry drove from a to b 12km away. Henry's average speed was 3km per hour faster than Harry's speed. If Henry reached b 8 minutes faster than Harry, what is Harry's

Question 1186166: Hi
Henry and Harry drove from a to b 12km away. Henry's average speed was 3km per hour faster than Harry's speed. If Henry reached b 8 minutes faster than Harry, what is Harry's average speed.
Thanks

Answer by ikleyn(52794) (Show Source): You can put this solution on YOUR website!
.
Henry and Harry drove from a to b 12km away. Henry's average speed was 3km per hour faster than Harry's speed.
If Henry reached b 8 minutes faster than Harry, what is Harry's average speed.
~~~~~~~~~~~~~~

Let x be the slower speed, in km/h.

Then the faster speed is (x+3) km/h.


Now you write the "time" equation


     -  =   of an hour.    (1)


Simplify it


     -  = 

     = 

     = 

    x*(x+3) = 15*18.


From this point, you  GUESS  the  ANSWER  MENTALLY  and momentarily:  x = 15 km/h.


ANSWER.  Harry's average speed is 15 km/h.


CHECK.   -  =  =  = ,   exactly as in equation (1).  ! Correct !

Solved.

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