Discussion
The time taken by a man to row his boat upstream is twice the time taken by him to row the same distance downstream. If the speed of the boat in still water is 42 kmph, find the speed of the stream?
Answer: C
With \( b \) the still-water speed and \( r \) the stream's,
\[ \text{downstream} = b + r, \qquad \text{upstream} = b - r \]
Twice the time means half the speed:
\[ \frac{b + r}{b - r} = 2 \quad\Longrightarrow\quad 42 + r = 2(42 - r) = 84 - 2r \]
\[ 3r = 42 \quad\Longrightarrow\quad r = 14 \text{ kmph} \]
Checking: 56 kmph downstream and 28 kmph upstream - exactly double. The rule \( r = \tfrac{b}{3} \) holds for any "twice as long" problem.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development