Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - General Questions (Q.No. 27)

Problems on Trains

27.

A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is:

45 m

50 m

54 m

72 m

Answer: Option

Explanation:

2 kmph =		2 x	5		m/sec =	5	m/sec.
			18			9

4 kmph =		4 x	5		m/sec =	10	m/sec.
			18			9

Let the length of the train be x metres and its speed by y m/sec.

Then,

= 9 and

= 10.

y -	5
	9

y -	10
	9

Therefore 9y - 5 = x and 10(9y - 10) = 9x

9y - x = 5 and 90y - 9x = 100.

On solving, we get: x = 50.

Therefore Length of the train is 50 m.

Discussion:

106 comments Page 7 of 11.

Shaela said: 9 years ago

Thank You @Anagha.

James said: 9 years ago

Good one @Kapil.

Ayesha said: 9 years ago

Excellent shortcut @Anagha.

S.Banerjee said: 9 years ago

Thanks for the shortcut method @Anagha.

S.Banerjee said: 9 years ago

Is there any shortcut method to solve this problem? Please help me if there is any shortcut to solve easily.

Vikas3692 said: 9 years ago

@Anagha,

Please explain why 9 * 10?

Mou444276 said: 9 years ago

@Anagha.

Why 9 *10 or not 19?

Anagha said: 9 years ago

(4-2) * (5/18) * 9 * 10 = 50.

Anu malik said: 9 years ago

Can't understand, please, tell me how to explain it in short cut method?

Sumaira said: 9 years ago

@Kapil.

Thanks for the trick I tried to simplify more.

(S - 2) * 5/18 = L/9..........(1)

Similarly
(S - 4) * 5/18 = L/10..........(2)

9(s - 2) = 10(s - 4)
9s - 18 = 10s - 40
S = 40-18
S = 22

Put value of s in any one equal , suppose in (1)
(22 - 2) * 5/18 = L/9.
L = 50.

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