SOLUTION: Please help me solve this! :) a car travelling at a uniform speed reached its distination which is 400 km away from the city. On the return trip, because of motor trouble, the spe

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Please help me solve this! :) a car travelling at a uniform speed reached its distination which is 400 km away from the city. On the return trip, because of motor trouble, the spe      Log On


   

Question 888126: Please help me solve this! :)
a car travelling at a uniform speed reached its distination which is 400 km away from the city. On the return trip, because of motor trouble, the speed is reduced to 10 miles per hour. This caused the car to stay on the road 2 hours longer. Find the speed of the car
please.
Answer by dkppathak(439) About Me  (Show Source):
You can put this solution on YOUR website!

a car travelling at a uniform speed reached its destination which is 400 km away from the city. On the return trip, because of motor trouble, the speed is reduced to 10 miles per hour. This caused the car to stay on the road 2 hours
distance =400 miles
let usual speed is X mile per hours
reduced speed due to motor trouble =X-10 miles per hours
time=distance/speed
t1= 400/x
t2= 400/X-10 as per given conditions t2-t1=2
400/X-400/X-10 =2 by LCM
400(X-10)-400X/X(X-10) =2
400 (x-x+10)/X^2-X =2
400x10/X^2-X=2 taking 2 common
2000/X^2-X =1
X^2-X-2000 =0 by factorization spiting middle term
X^-50X+40x-2000 =0
(X-50)(X+40)=0
X=50 or X=-40 speed can not be negative so neglecting -40
speed is 50 miles per hours