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:
233 comments Page 24 of 24.
RAHUL RAJ PRASAD said:
5 years ago
Train A length=x;time A=27;speed A=x/27.
Train B length=Y;time B=17;speed B=Y/17.
Now relative speed between train A and B is=(x+Y)/23.
Now we equating these equation through relative speed;
(x+Y)/23=x/27+Y/17.
=> (x+Y)/23=(17x+27Y)/459,
=>459x+459Y=391x+621Y,
=>68x=162Y,
=>x/Y=162/68,
=>(x/27)/(Y/17)=(162/27)/(68/17),
=>speed A/speed B=3/2,
=>speed A : speed B = 3:2.
Train B length=Y;time B=17;speed B=Y/17.
Now relative speed between train A and B is=(x+Y)/23.
Now we equating these equation through relative speed;
(x+Y)/23=x/27+Y/17.
=> (x+Y)/23=(17x+27Y)/459,
=>459x+459Y=391x+621Y,
=>68x=162Y,
=>x/Y=162/68,
=>(x/27)/(Y/17)=(162/27)/(68/17),
=>speed A/speed B=3/2,
=>speed A : speed B = 3:2.
Manoj said:
5 years ago
How possible 3:2?
Because the first train takes more time than the second one. But the speed ratio is 3:2. Actually the second train moves fast than first.
Because the first train takes more time than the second one. But the speed ratio is 3:2. Actually the second train moves fast than first.
Diya said:
5 years ago
Very nice explanation, Thanks @Poornima.
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