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 3 of 6.
Bhanu said:
8 years ago
Given speed in ratio : 7:8.
First speed = 7x.
Second speed = 8x.
7x/8x = x(?)/400/4.
7x/8x = x/100.
7x*100 = 8x*x.
700x = 8x*x.
Cancel x in both sides,
700 = 8x.
x = 700/8.
x = 87.5 km/hr.
First speed = 7x.
Second speed = 8x.
7x/8x = x(?)/400/4.
7x/8x = x/100.
7x*100 = 8x*x.
700x = 8x*x.
Cancel x in both sides,
700 = 8x.
x = 700/8.
x = 87.5 km/hr.
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?
Prajweetha said:
1 decade ago
Second train runs at 400kms in 4 hours, so in 1 hour its speed is 400/4=100kms/hr.
Let speed of first train be "x".
Ratio is 7:8=x:100.
Then 8x=7*100.
X=700/8.
=87. 5km/hr.
Let speed of first train be "x".
Ratio is 7:8=x:100.
Then 8x=7*100.
X=700/8.
=87. 5km/hr.
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)
Vellamuthu said:
1 decade ago
Ratio 7:8
Speed =400/4 km/hr
speed =x
x=400/4 km/hr
4x=400 km
Second train Ratio 8*50=400=4x
Ratio 7*50=4x
350=4x
x=350/4
x=350/4
x=87.5 km/hr
Speed =400/4 km/hr
speed =x
x=400/4 km/hr
4x=400 km
Second train Ratio 8*50=400=4x
Ratio 7*50=4x
350=4x
x=350/4
x=350/4
x=87.5 km/hr
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?
Asit said:
1 decade ago
Let the speed of 1st train is x km/hr
2nd train speed =distance/time
So 400/4=100km/hr
now given that their ratio= 7:8(i.e 1st/2nd)
so x/100 = 7/8
=>x=87.5km/hr
2nd train speed =distance/time
So 400/4=100km/hr
now given that their ratio= 7:8(i.e 1st/2nd)
so x/100 = 7/8
=>x=87.5km/hr
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)
Sivaprakash said:
3 years ago
Just consider 7:8.
X is speed of first flight.
Speed of the second S=D/S=400/4=100kmph;
8=100 and 7=?.
8/100=7/x=? Cross multiplicate.
100*7/8=87.5.
X is speed of first flight.
Speed of the second S=D/S=400/4=100kmph;
8=100 and 7=?.
8/100=7/x=? Cross multiplicate.
100*7/8=87.5.
(8)
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.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers