Two cars moving in the opposite directions, leave the same place at same time. The speed of one them is greater than that of the other by 5 miles per hour. They are at a distance of 50 miles from each other at the end of two hours. What is the speed of the car having a lower speed (in miles/hour).
Since the cars are moving in opposite directions, therefore Relative speed = Sum of speeds of both the cars. Now, Lets assume the speed of one car is x miles / hr and that of the second is (x+5) miles/ hr.
Relative Speed = x + (x+5) = 2x + 5 At this speed, they have created a gap of 50 miles in 2 hours. Thus, Total distance = 50 miles = R.S. X Time taken = (2x + 5) X 2 = 4x + 10 It gives, x = 10 miles/hr which is equal to the speed of car having a lower speed.
suppose cars A and B having speeds x and X+5 miles/hr respectively. After 2 hr distance travelled by A and B will be 2x and 2(x+5) miles respectively. Since both cars are travelling in opposite direction and distance between them after 2 hr is 50 miles… Therefore 2x + 2(x+5) = 50; 4x + 10 = 50; x = 10 So the speed of the car with lower speed will be 10 miles/hr
If the speed of the slower car is x mph, the speed of the other car is x+5 mph. So in two hours the distance between 2(2x+5)=4x+10 = 50. So x =10. Hence the speed of the slower car is 10 mph
I have one more question-- Suppose you were sitting inside this train.the train is moving at a speed of say 60 Kmph.Another train on a parallel track is moving at a speed 40 Kmph in the same direction as yours.There is a guy on the other train,the guy in the other train moves in the direction opposite to that of train themselves at the speed of 10Kmph.What is the relative speed of guy w.r.t you? Ans-3o Kmph
This is a pretty simple relative speed matter. Your train moves at 60 kph forward, and the other train moves at 40 kph forward. But the man is moving 10 kph backwards, so relative to the ground, the mean is actually moving at 40 + ( – 10 ) = 30 km forward. Now, relative to your train, since man is moving in the same direction but slower, it’ll actually seems like he’s moving backwards at 30 kph (60 – 30 = 30).
It’s a bit confusing to keep the + and – signs right, but if you think about it enough it makes sense.
Hey oLahav,
I have doubt that a man is moving @ 10 Kmph in a train which is moving @40 Kmph.So his relative speed should be added(40+10=50),as if two things are moving in opposite direction then their relative speed is the addition of their individual speed and vice versa.then why did you subracted 10 from 40.Pls correct me if i m wrong.
Since the man is said to be moving “in the direction opposite to that of the trains”, you would subtract his speed from that of the train. Or else say the train’s speed is 40, then since the man is moving “backwards” (relatively), his speed is negative 10, and 40 + ( – 10 ) = 30.
Think about this yourself- say you’re moving backwards on a train that moves forward. It will seem that you are moving forward but at a slower rate than the train, since you’re walking backwards. If you’d be moving forward, you would appear to move faster, and it that case the speeds would be added to 50.
pls sove these questions--
A certain cake recipe states that the cake should be baked in a pan 8 inches in diameter. If Jules wants to use the recipe to make a cake of the same depth but 12 inches in diameter, by what factor should he multiply the recipe ingredients?
pls sove this ques- A train travelling 50 Kmph meets with an accident and then proceed at3/4 of its former speed and arrives at its destination 35 min late. Had the accident occured 24 Km further,it would have reached the destination only 25 min late .The speed of train is?
Ans 48 Kmph
Thanks a lot sureshbala ..it really help me….
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