Aptitude - Time and Distance - Discussion

Speed = D/T.
i.e- 75/12.5 = 60km.
The speed is 50% more;
60 is 50% of 120 = 120 kmph.

50 % more means not 50/100. car has already 100 %.50 % more means 150/100

Car seed is 100.

So train speed in 50% more.

So it is 150/100.

I have an easier and simple solution.

The train is 50% faster than a car so for a 75km distance when the train reaches (without stopping) at B car will be some distance behind the train.

Well, train is 50% faster so the car should be at 50km when the train reaches point B (75km) (because 50 + 50% of 50 = 75).

And it's given that the train is 12.5 faster than a car (if it stops for 12.5 min and then after they reach at point B together).

Means rest of the distance (25km) car will cover in 12.5 min.

So, the speed of car = 50km/12. 5/60 hr = 120km/hr.

The speed of car be x km/h.
Then speed of the train will be = 3x/2km/h,
and the time taken to cover up 75 km is equal, but the train lost about 12.5 minutes while stopping at the stations.
So 75/x - 50/x = 5/24,
x= 120km/h.

Can you exlpain how 150x/100 came?

Hae even though its % it must me 50x/100 only na?

Can any one please tell me how that 125/(10x60) came?

Another shortcut yet simple method I would like to share wherein forget the hassle of x and y so the method is as follow:

Time taken by the car and train to reach the destination is the same and if you read the question carefully it is mentioned that the train has halted for 12.5 minutes at the stations that means just because of 12.5 minutes halt the train and the car covered 75 kilometers at the same time.

Just because of 12.5 minutes the train misses to cover 50% of the route that means the total time taken by the train and the car to reach the destination is 37.5 minutes ( working- 75km/2 =37.5, so in 12.5 minutes stop it missed 37.5km, hence the train took total 25 mins to reach the destination + 12.5 mins halt = 37.5 mins. )

Now comes the cross multiplication part. 37.5 mins = 75 kms
60 mins = ? (working- we already know how much kilometers it can cover in minutes but we want to find km/hour, so 1 hour = 60 mins.)
= (60*75)/37.5
=120.

To solve in this way you require a bit logic and good knowledge of cross multiplication. Still if you don't understand this method I suggest you to go for the Admins method.

75km/s * 60 second = 4500sec,
50%-12.5 the train lost =37.5,

Speed = Distance/time.

then 4500sec/37.5 = 120km.