<PRE><B>Question 888126</B>

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 


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