NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 03:52 It is currently 26 Apr 2024, 03:52
Decision Tracker
My Rewards
New posts
New comers' posts

Close
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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

A boat can cover a certain distance of 180 km and come back in 12.5 ho

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
TheNightKing
VP
VP
Joined: 18 Dec 2017
Posts: 1170
Own Kudos [?]: 991 [3]
Given Kudos: 421
Location: United States (KS)
GMAT 1: 600 Q46 V27
Send PM
A boat can cover a certain distance of 180 km and come back in 12.5 ho [#permalink] New post   25 Feb 2020, 10:48
2
Bookmarks
00:00
A
B
C
D
E

Difficulty:

55% (hard)

Question Stats:

62% (02:17) correct 38% (02:47) wrong based on 50 sessions
Hide Show timer Statistics
A boat can cover a certain distance of 180 km and come back in 12.5 hours. If the ratio of speed of boat in still water to speed of stream is 5:1, then find out the speed of boat in still water (in km/h)?
(a) 25 km/h
(b) 28 km/h
(c) 30 km/h
(d) 26 km/h
(e) 32 km/h
ShowHide Answer
Official Answer
C
User avatar
B
newyork2012
Manager
Manager
Joined: 22 Sep 2014
Posts: 126
Own Kudos [?]: 40 [0]
Given Kudos: 51
Location: United States (CA)
Send PM
GMAT ToolKit User
Re: A boat can cover a certain distance of 180 km and come back in 12.5 ho [#permalink] New post   25 Feb 2020, 21:06
Speed of stream x

180/(x+5x) + 180/(5x-x) = 12.5

12.5x=30+45
x=6
5x=30

Posted from my mobile device
User avatar
L
EgmatQuantExpert
e-GMAT Representative
Joined: 04 Jan 2015
Posts: 3726
Own Kudos [?]: 16843 [0]
Given Kudos: 165
Send PM
Re: A boat can cover a certain distance of 180 km and come back in 12.5 ho [#permalink] New post   28 Feb 2020, 05:46
Expert Reply

Solution – Using Options



Given
In this question, we are given that
    • A boat can cover a certain distance of 180 km and come back in 12.5 hours
    • The ratio of speed of boat in still water to speed of stream is 5:1

To find
We need to determine
    • The speed of the boat in still water (in kmph)

Approach and Working out
As the ratio of speeds is given as 5: 1, we can start with the options which are multiples of 5.

If speed of the boat in still water is 25, then speed of stream is 5
    • 180/(25 + 5) + 180/(25 – 5) = 180/30 + 180/20 = 6 + 9 = 15, which is not satisfying as the given total time is 12.5 hours

If speed of the boat in still water is 30, then speed of stream is 6
    • 180/(30 + 6) + 180/(30 – 6) = 180/36 + 180/24 = 5 + 7.5 = 12.5, which is satisfying as the given total time

Thus, option C is the correct answer.

Correct Answer: Option C
User avatar
L
EgmatQuantExpert
e-GMAT Representative
Joined: 04 Jan 2015
Posts: 3726
Own Kudos [?]: 16843 [2]
Given Kudos: 165
Send PM
Re: A boat can cover a certain distance of 180 km and come back in 12.5 ho [#permalink] New post   28 Feb 2020, 05:50
1
Kudos
1
Bookmarks
Expert Reply

Solution – Using Equation



Given
In this question, we are given that
    • A boat can cover a certain distance of 180 km and come back in 12.5 hours
    • The ratio of speed of boat in still water to speed of stream is 5:1

To find
We need to determine
    • The speed of the boat in still water (in kmph)

Approach and Working out
If we assume the speed of stream as V, then speed of boat in still water is 5V

Hence, we can write
    • 180/(5V + V) + 180/(5V – V) = 12.5
    Or, 180/6V + 180/4V = 12.5
    Simplifying, we get V = 6

Hence, speed of the boat in still water = 5V = 5 x 6 kmph = 30 kmph

Thus, option C is the correct answer.

Correct Answer: Option C
User avatar
L
Archit3110
GMAT Club Legend
GMAT Club Legend
Joined: 18 Aug 2017
Status:You learn more from failure than from success.
Posts: 8020
Own Kudos [?]: 4098 [0]
Given Kudos: 242
Location: India
Concentration: Sustainability, Marketing
GMAT Focus 1:
545 Q79 V79 DI73
GPA: 4
WE:Marketing (Energy and Utilities)
Send PM
GMAT ToolKit User CAT Tests
Re: A boat can cover a certain distance of 180 km and come back in 12.5 ho [#permalink] New post   28 Feb 2020, 09:02
TheNightKing wrote:
A boat can cover a certain distance of 180 km and come back in 12.5 hours. If the ratio of speed of boat in still water to speed of stream is 5:1, then find out the speed of boat in still water (in km/h)?
(a) 25 km/h
(b) 28 km/h
(c) 30 km/h
(d) 26 km/h
(e) 32 km/h


total speed ;
180/(6x)+180/(4x)= 12/5
x = 6 hrs
speed still water ; 5x; 5*6 ; 30 kmph
IMO C
GMAT Club Bot
gmatclubot
Re: A boat can cover a certain distance of 180 km and come back in 12.5 ho [#permalink]
28 Feb 2020, 09:02
Moderators:
Bunuel
Math Expert
92929 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions