<PRE><B>Question 689340</B>
If a car traveled 5kilometer an hour faster it would take one hour less to travel 210 km.
 what is the speed of the car and what time does it take?
:
Let s = actual speed of the car
then
(s+5) = the faster speed 
:
Write a time equation; time = dist/speed
:
Actual time - faster time = 1 hr
{{{210/s}}} - {{{210/((s+5))}}} = 1
Get rid of the denominators, multiply by s(s+5), results
210(s+5) - 210s = s(s+5)
210s + 1050 - 210s = s^2 + 5s
Arrange as a quadratic equation
0 = s^2 + 5s - 1050
Factors to
(s+35)(s-30) = 0
The positive solution
s = 30 km/h is the actual speed
Find the time
{{{210/30}}} = 7 hrs actual time
:
:
Confirm this by finding the time at the faster speed
210/35 = 6 hrs, 1 hr less</PRE>