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

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) (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


     -  =   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.

RELATED QUESTIONS
Mary makes monthly visits to her parents in Malacca, a distance of 240 km from... (answered by Theo,ikleyn,MathTherapy)

Doctor White leaves home to drive to a convention. She is traveling at 55miles/hour. She... (answered by ankor@dixie-net.com,Razzak Ahmed,Alan3354)

Vivian is walking to the hair dresser�s at 1.0 m/s when she glances at her watch and... (answered by ikleyn)

Sina has an appointment at 11:15 40 km from her home. She averaged 60km/h for the trip... (answered by josmiceli)

Hi, Every day Rachel walks 20 km at a certain speed. One day Rachel left 30 minutes late (answered by josgarithmetic,MathTherapy)

Erin rides her bike from home to school in 15 minutes. If she increases her speed by 5... (answered by josmiceli)

rosily traveled 36 km in a day on foot and released that 2 by 3 of her journey still... (answered by Fombitz)

Rachel is driving to an appointment. at her current speed she will be 11 minutes late and (answered by ewatrrr)

Each morning a waitress either walks, cycles or takes the bus to her workplace. The... (answered by ewatrrr)