Each of the questions consists of a question followed by three statements. You have to study the question followed by three statements and decide which of the statements is/are necessary to answer the questions.
What is the speed of the train ?
A. The train crosses a single pole in 13 sec.
B. The train crosses a platform of length 250 m in 27 seconds
C. The train crosses another train running in the same direction in 32 seconds.
Since, the length of the train is not given, statements I,II & III are not sufficient alone.
I & II : Let length of train = y and speed = x
$$\frac{y}{x}$$ = 13 [From I]
y = 13x
$$\frac{250+y}{x}$$ = 27 [From II and using y=13x]
x = $$\frac{250}{14}$$ = m/s
Thus, I & II together are sufficient.
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