Question

What is the speed of a bullet train A?

I. The relative speed of train A and another train B running in opposite direction is 120 kmph.

II. The train B crosses a signal post in 6.75 seconds.

• A. if the data in Statement I alone are sufficient to answer the question, while the data in Statement II alone are not sufficient to answer the question.
• B. if the data in Statement II alone are sufficient to answer the question, while the data in Statement I alone are not sufficient to answer the question.
• C. if the data either in Statement I or in Statement II alone are sufficient to answer the question.
• D. if the data even in both Statements I and II together are not sufficient to answer the question.
• E. if the data in both Statements I and II together are necessary to answer the question.

Answer 1

The correct option is D

if the data even in both Statements I and II together are not sufficient to answer the question.

Let the two trains of length `x' metres and `y' metres be moving in opposite directions at `u' m/s and `v' m/s.

Then, Statement I gives, u + v = 120.

Statement II gives, v = $\frac{y}{6.75}$ .

From these equations, we cannot obtain `u'.