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 4 of 6.
ASHWANI said:
7 years ago
Let Distance is 2D=D for the first halt+D for the second half.
Total time =10hr.
Time taken in first half+Time taken in second half=10hr so,
T1/2 + T/2=10 Now Time = distance/speed.
D/21 + D/24=10.
(D*24 + D*21)/21*24=10 solve it we get.
45x=5040 = D= 112 it is the time taken half journey.
2D=112*2=224km.
I HOPE YOU UNDERSTAND.
Total time =10hr.
Time taken in first half+Time taken in second half=10hr so,
T1/2 + T/2=10 Now Time = distance/speed.
D/21 + D/24=10.
(D*24 + D*21)/21*24=10 solve it we get.
45x=5040 = D= 112 it is the time taken half journey.
2D=112*2=224km.
I HOPE YOU UNDERSTAND.
Ravi said:
7 years ago
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.
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.
(1)
Soumya said:
7 years ago
s1: s2= 7: 8.
The speed of the second train = distance/time = 400/4 =100.
This 100 corresponds to 8.
7: 8 * 12.5 = 100
Since 7:8 is a ratio, it will get multiplied to the same number only, therefore 7 * 12.5 = 87.5.
The speed of the second train = distance/time = 400/4 =100.
This 100 corresponds to 8.
7: 8 * 12.5 = 100
Since 7:8 is a ratio, it will get multiplied to the same number only, therefore 7 * 12.5 = 87.5.
Divya said:
7 years ago
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.
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.
(1)
Neha said:
6 years ago
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.
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.
(1)
Ganga said:
6 years ago
@Anika.
The speed is 45 kmph.
The speed is 45 kmph.
Utkarsh kohapare said:
6 years ago
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.
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.
Sam said:
6 years ago
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.
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.
Nayan vekariya said:
6 years ago
Fast solve to other method :
Two train ratio 7:8
First train speed = 400 km /4 hour
= 100 km/h
Ratio 8 ---------------> 100 km
Ratio of 7 ------------> ?
7 *100 / 8 = 87.5 km/p.
That answer is 87.5.
Two train ratio 7:8
First train speed = 400 km /4 hour
= 100 km/h
Ratio 8 ---------------> 100 km
Ratio of 7 ------------> ?
7 *100 / 8 = 87.5 km/p.
That answer is 87.5.
(8)
Prabhat Kumar said:
6 years ago
Ratio of 1st & 2nd train = 7:8
Let speed of the first train x.
2nd train speed = 400/4 = 100km/hr.
And for 1st train.
7:8::x:100.
8x = 700.
X = 700/8 = 87.5 km/hr.
So 1st train speed 87.5 km/hr.
Let speed of the first train x.
2nd train speed = 400/4 = 100km/hr.
And for 1st train.
7:8::x:100.
8x = 700.
X = 700/8 = 87.5 km/hr.
So 1st train speed 87.5 km/hr.
(7)
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