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Each of the questions given below consists of three statements, numbered I, II and II respectively. Please read the question and the statements carefully and decide which of the statement(s) is/are necessary to answer the question.

1)

What is the length of the train X ?

I. Train X crosses a telegraph post in 20 seconds.

II. Train X crosses a platform of length 800 m in 100 seconds.

III. Train X passess through a tunnel 400 m long in 60 seconds.


A) I and either II or III only

B) II and III only

C) II and either I or III only

D) III and either I or II only

E) Any two of the three

Answer:

Option E

Explanation:

Time taken to cross a pole = Length pf train / Its speed 20 =lspeed

speed =l20 ---(1)

Time taken to cross a platform =l+800speed

100 =l+800speed speed =l+800100 ---(2)

Time taken to pass through a tunnel =(l+400)60

60 =l+400speed

speed =l+40060 ---(3)

Equating any two out of three will give us l.

Correct answer is (E).