Question

What is the speed of a running bullet train which takes 12 seconds to cross a signal post?

I. The length of the bullet train is 120 metres.

II. The bullet train takes 36 seconds to cross a platform of 240 metres.

• 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 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.

Speed of the train $=\frac{Lengthofthetrain}{Timetakentocrossthepost}=\frac{120}{12}m/s=10m/s.$

Thus, statement I alone gives the answer.

Time taken to cross a platform $=\frac{(Lengthofthetrain+Lengthofplatform)}{Speedofthetrain}$

$\Rightarrow Speed=\frac{\left(l+240\right)}{36}$

So, II alone does not give the answer.