SOLUTION: if a car travelled 5 kilometer an hour faster it would take one hour les to travel 210 km.What is the speed of car and what time does it take.

Question 518908: if a car travelled 5 kilometer an hour faster it would take one hour les to travel 210 km.What is the speed of car and what time does it take.
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
original time - time after speed increase =1
t=d/r
d=210
r=x
210/x -210/(x+5)=1
multiply by the LCD x(x+5)
210(x+5)-240x=x(x+5)
210x+1050-210x=x^2+5x
x^2+5x-1050=0
Find the roots of the equation by quadratic formula

a= 1 , b= 5 , c= -1050

b^2-4ac= 25 + 4200
b^2-4ac= 4225

x1=( -5 + 65 )/ 2
x1= 30
x2=( -5 -65 ) / 2
x2= -35
Ignore negative value
speed = 30 mph
m.ananth@hotmail.ca
RELATED QUESTIONS
if a car travelled 5 kilometers an hour faster it would take an hours less to travel 210... (answered by mananth)

Please help me solve this question: If a car traveled 5kilometer an hour faster it would (answered by ankor@dixie-net.com)

If a train travels 5 km/h faster than its normal speed, it would take 1 hour less to... (answered by lwsshak3)

The car travelled to one place to anohter place 15 KM/hour and retrun to origin place 10... (answered by ewatrrr)

Two cars leaving the same spot going in the same direction. One car is traveling at the... (answered by richwmiller)

A car made a journey of 144 miles, stopping for one hour along the way. Had it travelled... (answered by ankor@dixie-net.com)

5. If a car travels at 60 km/hour for 2 hours, how far would the car have travelled? How... (answered by srinivas.g)

Car A left Melbourne for Adelaide at 11.00 a.m. and travelled at an average speed of 70... (answered by richwmiller)

If a car driver travelled 3 km in 2 hours then stopped for a one hour rest and then... (answered by ankor@dixie-net.com)