Two trains passing in the same and in opposite directions: speeds or their ratio

This type of question, asked 3 times: CDS 1 2018, CDS 1 2023, CDS 2 2024. All 3 questions below, oldest first.

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Question 1
CDS 1 2018
40 $A passenger train and a goods train are running in the same direction on parallel railway tracks. If the passenger train now takes three times as long to pass the goods train, as when they are running in opposite directions, then what is the ratio of the speed of the passenger train to that of the goods train? (Assume that the trains run at uniform speeds)$
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Question 2
CDS 1 2023
10 $The time taken by a train to cross a man travelling in another train is 10 seconds, when the other train is travelling in the opposite direction. However, it takes 20 seconds, if both the trains are travelling in the same direction. The length of the first train is 200 m and that of the second train is 150 m. What is the speed of the first train?$
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Question 3
CDS 2 2024
9 $X$
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Question 1