Question

What is the speed of the boat in still water?
I. It takes 2 hours to cover the distance between A and B downstream.
II. It takes 4 hours to cover the distance between A and B upstream.

• A. Data in the statement I alone are sufficient to answer the question, while the data in statement II alone are not sufficient to answer the question.
• B. 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. Data either in statement I alone or in statement II alone is sufficient to answer the question.
  
• D. Data given in both the statements I and II together are not sufficient to answer the question.
• E. Data in both the statements I and II together are necessary to answer the question.

Answer 1

The correct option is D Data given in both the statements I and II together are not sufficient to answer the question.

Let the distance between A and B be z km.
Again, let the speed of the boat in still water be x kmph and that of the stream be y kmph.
$\therefore$ Rate downstream = (x+y) kmph
Rate upstream = (x-y) kmph
From statement I,
$\frac{z}{x+y}=2\dots \left(i\right)$
From statement II,
$\frac{z}{x-y}=4\dots \left(ii\right)$
We have two equations and three variables, therefore both equations are not sufficient.