Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 4)
4.
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:
Answer: Option
Explanation:
Let the speeds of the two trains be x m/sec and y m/sec respectively.
Then, length of the first train = 27x metres,
and length of the second train = 17y metres.
 |
27x + 17y | = 23 |
| x+ y |
27x + 17y = 23x + 23y
4x = 6y
| |
x | = | 3 | . |
| y | 2 |
Discussion:
239 comments Page 1 of 24.
DHANASURIYA M G said:
2 months ago
Step 1: Express lengths in terms of speed and time.
Train 1 crosses a man in 27 seconds:
L1 = 27x.
Train 2 crosses a man in 17 seconds: L2 = 17y.
Step 2: Use the time to cross each other.
When trains move in opposite directions, their relative speed is x+y.
They cross each other in 23 seconds, so:
L1 + L2 = (x+y) × 23.
Substitute L1 and L2: 27x + 17y = 23(x+y)
Step 3: Simplify the equation
27x + 17y = 23x + 23y⟹
4x = 6y⟹x/y = 3/2.
Train 1 crosses a man in 27 seconds:
L1 = 27x.
Train 2 crosses a man in 17 seconds: L2 = 17y.
Step 2: Use the time to cross each other.
When trains move in opposite directions, their relative speed is x+y.
They cross each other in 23 seconds, so:
L1 + L2 = (x+y) × 23.
Substitute L1 and L2: 27x + 17y = 23(x+y)
Step 3: Simplify the equation
27x + 17y = 23x + 23y⟹
4x = 6y⟹x/y = 3/2.
(14)
Konatham preetham said:
6 months ago
@All.
You can solve alligation like take right side top 27 left side top take 17 middle of the alligation is 23 (17-23 = 6) and (27-23 = 4) and 2:3 inversely proportion 3:2 So, you can solve like only same like sec or km/hr or litres or kgs same terms you can solve like that.
You can solve alligation like take right side top 27 left side top take 17 middle of the alligation is 23 (17-23 = 6) and (27-23 = 4) and 2:3 inversely proportion 3:2 So, you can solve like only same like sec or km/hr or litres or kgs same terms you can solve like that.
(27)
Venkatesh said:
10 months ago
Let speeds be x and y.
Then, l1 = x * 27.
l2 = y * 17.
Time taken to cross each other = 23 seconds.
=> (l1+l2)/(x+y) = 23 seconds.
=> 27x + 17y = 23x + 23y.
=> x : y = 3:2.
Then, l1 = x * 27.
l2 = y * 17.
Time taken to cross each other = 23 seconds.
=> (l1+l2)/(x+y) = 23 seconds.
=> 27x + 17y = 23x + 23y.
=> x : y = 3:2.
(14)
Student said:
11 months ago
A train takes 27 sec to reach man and 23 sec to cross train B, so the difference is 4 sec
B train takes 17 sec to reach the man and 23 sec to cross train A, so the difference is 6 sec.
Speed is inversely proportional to time, so the ratio of speed is 6:4.
So 3:2 is the answer.
B train takes 17 sec to reach the man and 23 sec to cross train A, so the difference is 6 sec.
Speed is inversely proportional to time, so the ratio of speed is 6:4.
So 3:2 is the answer.
(159)
ARUN said:
11 months ago
I do not understand this. Please explain to me.
(12)
Anome said:
12 months ago
Very useful. Thanks all.
(12)
Dripta Majumdar said:
1 year ago
Why is the length of the platform not taken into consideration? Anyone, please explain to me.
(11)
Thavapriya A said:
1 year ago
How to solve the following step?
27x+17y =23x+23y.
Could anyone tell me please?
27x+17y =23x+23y.
Could anyone tell me please?
(24)
SAURABH PANDEY said:
2 years ago
Very well done. Thanks.
(8)
Samiddho said:
2 years ago
Time taken by train 1 = 27s.
Time taken by train 2 = 17s.
Time taken for them to cross each other = 23s
Let the velocity of train 1 be v1 and that of train 2 is v2, and their lengths be l1 and l2 resp.
Net velocity when they cross each other v = v1 + v2.
Thus;
(l1+l2) = (v1+v2)x23---> i
and
l1 = v1 * 27 and l2 = v2 * 17---> ii
By Replacing ii in i.
27v1 + 17v2 = 23(v1+v2)
4v1 = 6v2
v1:v2 = 3:2.
Time taken by train 2 = 17s.
Time taken for them to cross each other = 23s
Let the velocity of train 1 be v1 and that of train 2 is v2, and their lengths be l1 and l2 resp.
Net velocity when they cross each other v = v1 + v2.
Thus;
(l1+l2) = (v1+v2)x23---> i
and
l1 = v1 * 27 and l2 = v2 * 17---> ii
By Replacing ii in i.
27v1 + 17v2 = 23(v1+v2)
4v1 = 6v2
v1:v2 = 3:2.
(50)
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