Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
134 views
in Distance, Time and Speed by (237k points)
closed by
A boat with a speed of 21 km/hr in still water, travels from point A to B in the downstream direction and returns to point A. Another boat with speed of 28 km/hr travels from B to A and returns to point B. The difference between the time taken by them to cover the distance is 6.5 hrs. What is the distance between points A and B, if the speed of stream is 7 km/hr?
1. 420 km
2. 120 km
3. 280 km
4. 350 km
5. 210 km

1 Answer

0 votes
by (239k points)
selected by
 
Best answer
Correct Answer - Option 5 : 210 km

Speed of first boat from point A to B in downsream direction = 21 + 7 = 28 km/hr

Speed of first boat from point B to A(upstream) = 21 – 7 = 14 km/hr

Let the distance between A to B = D

Total time taken to complete this distance by first boat

⇒ (D/28) + (D/14) = 3D/28

Speed of second boat from point B to A in upstream direction = 28 – 7 = 21 km/hr

Speed of second boat from point A to B(downstream) = 28 + 7 = 35 km/hr

Total time taken to complete this distance by second boat

⇒ (D/21) + (D/35) = 8D/105

According to question,

(3D/28) – (8D/105) = 6.5

⇒ (45D – 32D)/420 = 6.5

⇒ D = 210

∴ The distance between points A and B is 210 km

 

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.

...