SOLUTION: when a bicyclist is 20 km from her destination she realizes that she will be 10 minutes late unless she increases her speed by 10 km. What is her current speed

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: when a bicyclist is 20 km from her destination she realizes that she will be 10 minutes late unless she increases her speed by 10 km. What is her current speed      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 1167533: when a bicyclist is 20 km from her destination she realizes that she will be 10 minutes late unless she increases her speed by 10 km. What is her current speed
Answer by ikleyn(52803) About Me  (Show Source):
You can put this solution on YOUR website!
.

The current speed = x  km/h.


The increased speed = (x+20)  km/h


The "time" equation is


    20%2Fx - 20%2F%28x%2B20%29 = 1%2F6  of an hour (which is 10 minutes).


Multiply both sides by 6x*(x+20).  You will get


    120*(x+20) - 120*x = x*(x+20)

    120x + 2400 - 120x = x^2 + 20x

    x^2 + 20x - 2400 = 0

    (x+60)*(x-40) = 0


Of the two roots, -60 and 40, only positive is meaningful.


ANSWER.  The current speed is 40 km/h.

Solved.