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Krunaal
The direct formula for this is, whenever two entities starting from opposite ends at the same time meet at a common point and the total distance they travelled is D, the ratio of their speeds \(\frac{Sa}{Sb} = \sqrt{\frac{Tb}{Ta}}\), where Tb and Ta is the time taken to reach their destination from the common point. Below is the detailed solution,

Let total distance be D, where D = d1 + d2

When Ram and Rahim meet, Ram covers d1 and Rahim covers d2

Speed of Ram = Sa; Speed of Rahim = Sb

We need to find \(\frac{Sa}{Sb}\)

When Ram and Rahim meet,

\(\frac{d1}{Sa} = \frac{d2}{Sb}\) ...............................(as time is same)

\(\frac{d1}{d2} = \frac{Sa}{Sb}\) .................................(1)

Ram takes 1 minute to cover d2, so \(Sa * 1 = d2\)

Rahim takes 4 minutes to cover d1, so \(Sb * 4 = d1\)

Subs. in (1)

\(\frac{Sb*4}{Sa*1} = \frac{Sa}{Sb}\)

\(4*Sb^2 = Sa^2\)

\(\frac{Sa}{Sb} = \frac{2}{1}\)

Answer B.
Hey could you elaborate why have you taken d2 as distance covered by ram in substitution? His distance initially assumed is d1 right?
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I ended up with t+4/t+1.. (where t is the time from start to the point ram and rahim cross each other)
I spent some time trying to understand if there was a way to eliminate t completely and reach the ratio but couldn't. I ended up marking 2 as substituting t = 1 results in 2, but I was confused by the root(2) [~1.4] option as well.. the other options I was able to cancel out as you cannot get those values with a t+4 / t+1 ratio ..
Is there a better/alternate way to approach this question ?
you were going correct. Refer to the post for meeting time forumla. https://gmatclub.com/forum/trains-a-and ... l#p3455145

meeting time \( t = \sqrt{4*1} = 2\)

Tram = Time taken by Ram to complete route = t + 1 = 3 min
Trah = Time taken by Rahim to complete route = t + 4 = 6 min

now we know speed is inversely proportional to time,

Therfore, \(\frac{Sram}{Srah}= \frac{Trah}{Tram} = \frac{6}{3} = 2\)

Answer is B.
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Sure, after Ram and Rahim meet at a common point, Ram has to cover the distance Rahim had covered from Point B i.e. d2 and Rahim has to cover the distance Ram had covered from Point A i.e. d1, hence the interchange. Hope it is clear.
sarthak1701
Krunaal
The direct formula for this is, whenever two entities starting from opposite ends at the same time meet at a common point and the total distance they travelled is D, the ratio of their speeds \(\frac{Sa}{Sb} = \sqrt{\frac{Tb}{Ta}}\), where Tb and Ta is the time taken to reach their destination from the common point. Below is the detailed solution,

Let total distance be D, where D = d1 + d2

When Ram and Rahim meet, Ram covers d1 and Rahim covers d2

Speed of Ram = Sa; Speed of Rahim = Sb

We need to find \(\frac{Sa}{Sb}\)

When Ram and Rahim meet,

\(\frac{d1}{Sa} = \frac{d2}{Sb}\) ...............................(as time is same)

\(\frac{d1}{d2} = \frac{Sa}{Sb}\) .................................(1)

Ram takes 1 minute to cover d2, so \(Sa * 1 = d2\)

Rahim takes 4 minutes to cover d1, so \(Sb * 4 = d1\)

Subs. in (1)

\(\frac{Sb*4}{Sa*1} = \frac{Sa}{Sb}\)

\(4*Sb^2 = Sa^2\)

\(\frac{Sa}{Sb} = \frac{2}{1}\)

Answer B.
Hey could you elaborate why have you taken d2 as distance covered by ram in substitution? His distance initially assumed is d1 right?
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d2 is the remaining distance he will be covering, it is denoted as d2 because that is equivalent to the distance that was covered by Rahim (as they were running towards each other and met at the common point, so distance covered by Rahim is equal to distance pending to be covered by Ram and vice versa)
sarthak1701
Krunaal
The direct formula for this is, whenever two entities starting from opposite ends at the same time meet at a common point and the total distance they travelled is D, the ratio of their speeds \(\frac{Sa}{Sb} = \sqrt{\frac{Tb}{Ta}}\), where Tb and Ta is the time taken to reach their destination from the common point. Below is the detailed solution,

Let total distance be D, where D = d1 + d2

When Ram and Rahim meet, Ram covers d1 and Rahim covers d2

Speed of Ram = Sa; Speed of Rahim = Sb

We need to find \(\frac{Sa}{Sb}\)

When Ram and Rahim meet,

\(\frac{d1}{Sa} = \frac{d2}{Sb}\) ...............................(as time is same)

\(\frac{d1}{d2} = \frac{Sa}{Sb}\) .................................(1)

Ram takes 1 minute to cover d2, so \(Sa * 1 = d2\)

Rahim takes 4 minutes to cover d1, so \(Sb * 4 = d1\)

Subs. in (1)

\(\frac{Sb*4}{Sa*1} = \frac{Sa}{Sb}\)

\(4*Sb^2 = Sa^2\)

\(\frac{Sa}{Sb} = \frac{2}{1}\)

Answer B.
Hey could you elaborate why have you taken d2 as distance covered by ram in substitution? His distance initially assumed is d1 right?
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