LIVE Course for free

Rated by 1 million+ students
Get app now
0 votes
31 views
in Distance, Time and Speed by (59.9k points)
closed by
A boat travels 20 km upstream in 10 hours and 72 km downstream in 8 hours. What is the speed of a boat in still water?
1. 5.5 kmph
2. 11/7 kmph
3. 6 kmph
4. 5 kmph

1 Answer

0 votes
by (110k points)
selected by
 
Best answer
Correct Answer - Option 1 : 5.5 kmph

Given:

u/s = 20 km in 10 hours

Ds = 72 kms in 8 hours

Formula used:

If speed in upstream in X kmph and downstream is Y kmph

Speed in still water = (1/2)(X + Y) kmph

Rate of stream = (1/2)(X – Y) kmph

Calculations:

Speed of upstream and downstream

⇒ Speed of upstream = 20 / 10

⇒ Speed of upstream = 2 kmph

⇒ Speed of downstream = 72 / 8

⇒ Speed of downstream = 9 kmph

⇒ speed in still water = (1/2)(2 + 9)

⇒ Speed in still water = 11/2 kmph

Speed in still water is 5.5 kmph

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

...