Events & Promotions
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Sep 2107:00 PM EDT
-10:00 PM EDT
Boost your GMAT score in less than one month in a live online class + 6 months access to TTP OnDemand video courses included!
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
43% (02:43) correct
57%
(02:43)
wrong
based on 87
sessions
History
Date
Time
Result
Not Attempted Yet
A man is travelling on a boat upstream a certain river. When he goes under a bridge he is distracted and drops a bottle of whisky into the water without realising. The bottle floats downstream while the man travels upstream for 20 minutes. Then he realises that he had dropped the bottle. He turns back (neglect the time for this operation) and travels downstream at the same speed in respect to the water. He reaches the bottle 1 kilometre downstream from the bridge. What is the speed of the water of the river in km/h?
A. 1 km/h
B. 1.5 km/h
C. 2 km/h
D. 2.5 km/h
E. 3 km/h
_________________
A. 1 km/h
B. 1.5 km/h
C. 2 km/h
D. 2.5 km/h
E. 3 km/h
_________________
New to the GMAT Club?
- • Questions: Question Bank | Bunuel's Signature Collection
• Tests: GMAT Club Tests | Forum Quiz
• Guides: Quantitative | Critical Reasoning | Reading Comprehension | Ultimate Quant Guide | All You Need for Quant
• Rules: Quantitative | Verbal
Rm = boat speed
Rw = water speed
He heads upstream for 20 minutes at a speed of Rm-Rw before turning around, so he travels upstream:
20(Rm-Rw)
The bottle has traveled
20Rw downstream in that 20 minutes
Upon turning around, the man has to travel the distance between him and the bottle and is now going at a speed of Rm + Rw, with distance of:
20(Rm-Rw)+ 20Rw
and is closing in on the bottle at a speed represented by their difference in speeds:
(Rm+Rw)-Rw
So the time to cover this distance is distance/rate:
t = [20(Rm-Rw) + 20Rw]/[(Rm+Rw)-Rw] =
20Rm/Rm = 20 minutes
So the man travels downstream for the same amount of time he traveled upstream !
So the total time elapsed is
40 minutes,
during which time the bottle has traveled 1km downstream.
So the rate of speed of the stream must be:
1/(40/60) = 3/2 = 1.5km/hr
Posted from my mobile device
Rw = water speed
He heads upstream for 20 minutes at a speed of Rm-Rw before turning around, so he travels upstream:
20(Rm-Rw)
The bottle has traveled
20Rw downstream in that 20 minutes
Upon turning around, the man has to travel the distance between him and the bottle and is now going at a speed of Rm + Rw, with distance of:
20(Rm-Rw)+ 20Rw
and is closing in on the bottle at a speed represented by their difference in speeds:
(Rm+Rw)-Rw
So the time to cover this distance is distance/rate:
t = [20(Rm-Rw) + 20Rw]/[(Rm+Rw)-Rw] =
20Rm/Rm = 20 minutes
So the man travels downstream for the same amount of time he traveled upstream !
So the total time elapsed is
40 minutes,
during which time the bottle has traveled 1km downstream.
So the rate of speed of the stream must be:
1/(40/60) = 3/2 = 1.5km/hr
Posted from my mobile device
b- velocity of boat
w- velocity of water/ bottle
d- distance travel by boat from bridge upto point it travel upsteam( for 20 min)
d=(b-w)*20/60 km = (b-w)/3
time taken by bottle to travel 1km = time taken by boat to travel (distance 'd' upsteam+ distance 'd' downsteam+ 1 km downsteam)
(1/w)= d/(b-w) + d/(b+w) + 1/(b+w)
(b-w)(b+w)= (db+dw+db-dw+b-w)*w
b^2-w^2=(2db+b-w)*w
b^2-w^2= 2dbw+bw-w^2
b=w(2d+1)
resolve equation and put value of d
w=1.5 km/hr
w- velocity of water/ bottle
d- distance travel by boat from bridge upto point it travel upsteam( for 20 min)
d=(b-w)*20/60 km = (b-w)/3
time taken by bottle to travel 1km = time taken by boat to travel (distance 'd' upsteam+ distance 'd' downsteam+ 1 km downsteam)
(1/w)= d/(b-w) + d/(b+w) + 1/(b+w)
(b-w)(b+w)= (db+dw+db-dw+b-w)*w
b^2-w^2=(2db+b-w)*w
b^2-w^2= 2dbw+bw-w^2
b=w(2d+1)
resolve equation and put value of d
w=1.5 km/hr
Moderator:
Announcements
Monday, Sep 14, 2026
11:30am NY / 3:30pm London / 9pm Mumbai
Subscribe to GMAT Club for New Podcast Episodes, Debriefs, & Insightful Sessions on GMAT Preparation
Tuck at Dartmouth
AI at Dartmouth Tuck: How the School Is Preparing Leaders for the Age of Artificial Intelligence
Inside the courses, research, and hands-on learning defining wise, decisive leadership in an AI-driven world.
Read More
Inside the courses, research, and hands-on learning defining wise, decisive leadership in an AI-driven world.
Read More
Top 5 GMAT Debrief Videos
Success stories and strategies from high-scoring candidates.