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sunil gupta

· started a discussion

· 1 Months ago

please describe this answer (Question: 127794.0 )

this question please describe

Question:

A goods train and a passenger train are running on parallel tracks in the same direction. The driver of the goods train observes that the passenger train coming from behind overtakes and crossed is train completely in 60 seconds. Whereas a passenger on the passenger train marks that he crossed the goods train in 40 seconds. If the speed of the trains be in the ratio of 1: 2, find the ratio of their lengths.

Options:
A)

1:2

B)

2:1

C)

3:2 

D)

2:3

E)

None of these

Solution:

(Both travelling in same direction)

Relative Speed = S1 - S2

S1 - S2  = (d1 + d2) / 60

S1 - S2  =  d1 / 40  

 Divide both you get d2 / d1 = 1:2

             Therefore  d1/d2 = 2:1


Alternate method- 


Let the speeds of the two trains be s and 2s m/s respectively.
Also, suppose that the lengths of the two trains are P and Q metres respectively.


Then, 

=\(\cfrac{P+Q}{2s-s}=60\) -------- (i)
and 

= \(\cfrac{P}{2s-s}=40\)-------- (ii)

On dividing these two equation we get:

\(\cfrac{(P+Q)}{P}=\cfrac{60}{40} \)

P : Q = 2 : 1

Knowledge Expert

· commented

· 1 Months ago

Dear Student, explanation has been provided.Do re-read it.Keep Learning with Us.
Best Wishes.
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