Aptitude - Time and Distance - Discussion
Discussion Forum : Time and Distance - General Questions (Q.No. 8)
8.
The ratio between the speeds of two trains is 7 : 8. If the second train runs 400 km in 4 hours, then the speed of the first train is:
Answer: Option
Explanation:
Let the speed of two trains be 7x and 8x km/hr.
| Then, 8x = |  |
400 |  |
= 100 |
| 4 |
 x = |
|
100 | |
= 12.5 |
| 8 |
Speed of first train = (7 x 12.5) km/hr = 87.5 km/hr.
Discussion:
51 comments Page 5 of 6.
Arun said:
1 decade ago
Easy way is here.
We know that ratio of two train is = 7:8.
Speed of 1st train = ?
Speed of 2nd train = 400\4 = 100 kmphr.
So, 1st train:2nd train = 7:8.
? : 100.
So divide 100 by 8 we will get = 12.5.
Now multiply 1st train ratio with 12.5.
i.e 12.5*7 = 87.5.
So the speed of first train = 87.5 kmphr.
We know that ratio of two train is = 7:8.
Speed of 1st train = ?
Speed of 2nd train = 400\4 = 100 kmphr.
So, 1st train:2nd train = 7:8.
? : 100.
So divide 100 by 8 we will get = 12.5.
Now multiply 1st train ratio with 12.5.
i.e 12.5*7 = 87.5.
So the speed of first train = 87.5 kmphr.
Pratibha said:
1 decade ago
The answer and the method to solve is right but is their ratio is right? NO.
Because 87.5/100 is not equal to 7:8.
87.8/100 = 0.87.
Why? Can anyone answer my question?
Because 87.5/100 is not equal to 7:8.
87.8/100 = 0.87.
Why? Can anyone answer my question?
Raghu said:
10 years ago
400/4 = 100 km/hr.
8/7 = 100/x.
x = 87.5.
8/7 = 100/x.
x = 87.5.
Nasir said:
9 years ago
If a person drives from point A to B with the speed of 40 km/hr and returns on the same path with the speed of 80 km/hr. Find the average speed of a person?
Can anyone solve this problem?
Can anyone solve this problem?
Sri said:
9 years ago
Here is the simple method :
400/8 = 50.
400 - 50 = 350.
350/4 = 87.5.
400/8 = 50.
400 - 50 = 350.
350/4 = 87.5.
Sai said:
9 years ago
Thank you all for explaining the solution in different ways.
Anika said:
9 years ago
@Nasir.
I also did not understand how to solve the problem.
Can anyone find the solution for Nasir's question.
I also did not understand how to solve the problem.
Can anyone find the solution for Nasir's question.
Anika said:
9 years ago
The odometer of a car reads 57321.0 km when the clock shows time 8.30am. What is the distance moved by a car at 8.50 am, the odometer reading has changed to 57336.0km. Calculate the speed of the car and express the speed in km/hr.
Solve and find the solution.
Solve and find the solution.
Dev said:
8 years ago
@Anika.
The speed is 1927. Is it right?
The speed is 1927. Is it right?
Sree said:
8 years ago
Ratio of train speed = 7:8.
Second train = 400 in 4 hours,
Speed = 100km/h,
8x = 100,
x = 100÷8 = 25/2,
Then, 7x = 25/2 * 7,
=175/2 = 87.5.
Second train = 400 in 4 hours,
Speed = 100km/h,
8x = 100,
x = 100÷8 = 25/2,
Then, 7x = 25/2 * 7,
=175/2 = 87.5.
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