Aptitude - Time and Distance - Discussion

@All.

The ratio is7:8::x:400.
Simply multiply extremes(400*7) and divide by 8x(mean).
400*7=2800÷8,
=350.
Now 350÷4=87.5.

Simple, just consider their ratios and equate :
S1:S2 = 7:8.

Let's consider x is the speed of train1;
x/8 = 7/88x= 700.
x= 700/8 = 87.5.

The right answer is 87.5 km/hr.

How to solve problem which is given in ratio? Any specific formula for that?

Hey guys can anyone help me to solve this problem?

Nilesh goes to school from the village at the speed of 4km/hr and returns at the speed of 2km/hr. Find the distance from his village to the school.

Given 7:8.

We need the speed of the first train so make it 1 for simple calculations.
1:8/7,
400km in 4hr then 100km in 1hr.
so 100km/hr,
100 = 8x/7 = 87.5.

Let the speed of two trains be 7x and 8x km/hr.

Then, 8x =400/4= 100.
8x = 100.
x = 100/8.
x = 12.5.

So,
Speed of first train = (7 x 12.5) km/hr = 87.5 km/hr =>Ans.

It's easy to solve when we go by options.
In question, they have given details about the second train. Now using formula s=d/t ,we get s=400/4=100.

First train speed is not known, but the ratio of speeds is given in question as 7:8.
We got second trains speed i.e 100,

Now let's look into the options (the options tell about first trains speed ) and when we take the last option 87.5:100 (//speed of first train: speed of the second train ) we get 7:8.Thus concluded that the last option is right.:)

We can calculate this by a simple method.

Here the distance = 400 km.

And the time taken to cover this distance by the second train is 4 h.

Therefore the speed of the second train will be 400/4 = 100 kmph.

The ratio of the speed of both the trains is 7:8.

Therefore the speed of 1st train will be 100*7/8.

= 700/8.

= 87.5.

So the speed of the 1st train is 87.5 kmph.

Simply;

Speed=distance/time.
s=400/4 i.e = 100kmph speed of second train.

The ratio is 7:8
Therefore 8 ------> 100
7 ------> x.

Solving it we get 8x=700.
x = 700/8 = 87.5.