Welcome! Check out our free B-School Guides to learn how you compare with other applicants.

## Ratio

This topic has 2 expert replies and 7 member replies
bobdylan Rising GMAT Star
Joined
30 Nov 2011
Posted:
68 messages
Ratio Tue Jun 12, 2012 5:19 am
Elapsed Time: 00:00
• Lap #[LAPCOUNT] ([LAPTIME])
At a pet center 5 cans of food are used in 6 days to feed 10 dogs. Each dog is provided with the same amount of food. How many cans of food would be needed for 12 days if 3 of the dogs were sold?
a.84
b. 70
c. 49
d. 25
e. 24

Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
Ashujain Really wants to Beat The GMAT!
Joined
20 Apr 2012
Posted:
123 messages
Followed by:
1 members
Thanked:
28 times
Tue Jun 12, 2012 6:20 am
bobdylan wrote:
At a pet center 5 cans of food are used in 6 days to feed 10 dogs. Each dog is provided with the same amount of food. How many cans of food would be needed for 12 days if 3 of the dogs were sold?
a.84
b. 70
c. 49
d. 25
e. 24
Are you sure that the answer choices provided are correct?

Because I am getting 7 cans as answer. below is my explanation:

Cans of food consumed by 1 dog in 1 day = 5/(10*6) = 1/12
Therefore, Cans of food consumed by 7 dogs in 12 days = 1/12 * 12 * 7 = 7

Thanked by: gmattesttaker2
bobdylan Rising GMAT Star
Joined
30 Nov 2011
Posted:
68 messages
Tue Jun 12, 2012 7:23 am
Sorry, it was 35 cans of food!
At a pet center 35 cans of food are used in 6 days to feed 10 dogs. Each dog is provided with the same amount of food. How many cans of food would be needed for 12 days if 3 of the dogs were sold?
a.84
b. 70
c. 49
d. 25
e. 24

bobdylan Rising GMAT Star
Joined
30 Nov 2011
Posted:
68 messages
Tue Jun 12, 2012 7:24 am
Sorry, it was 35 cans of food!
At a pet center 35 cans of food are used in 6 days to feed 10 dogs. Each dog is provided with the same amount of food. How many cans of food would be needed for 12 days if 3 of the dogs were sold?
a.84
b. 70
c. 49
d. 25
e. 24

Ashujain Really wants to Beat The GMAT!
Joined
20 Apr 2012
Posted:
123 messages
Followed by:
1 members
Thanked:
28 times
Tue Jun 12, 2012 10:53 pm
Then the answer would be 49.

Let me know if my solution is not clear to you.

hey_thr67 Really wants to Beat The GMAT!
Joined
15 Feb 2011
Posted:
299 messages
Followed by:
2 members
Thanked:
9 times
Wed Jun 13, 2012 3:41 am
IMO C:

Solution is,

Number of cans required for 12 days = 35 x (7/10) x (12/6) = 49

### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
Joined
25 May 2010
Posted:
6092 messages
Followed by:
1039 members
Thanked:
5258 times
GMAT Score:
790
Wed Jun 13, 2012 3:58 am
bobdylan wrote:
At a pet center 35 cans of food are used in 6 days to feed 10 dogs. Each dog is provided with the same amount of food. How many cans of food would be needed for 12 days if 3 of the dogs were sold?
a.84
b. 70
c. 49
d. 25
e. 24
The amount of food needed is VARIABLE: it depends on the number of dogs and the number of days.
Food = dog*days.

But the amount of food PER CAN is CONSTANT: it remains the same value, regardless of the number of dogs or the number of days.
(dogs*days)/cans = k.

Since the amount of food per can must always be the same value, we get the following:
(dogs*days)/cans = (dogs*days)/cans.

Thus, given that 10 dogs over 6 days require 35 cans and that 7 dogs over 12 days require x cans, we get:
(10*6)/35 = (7*12)/x
x = 49.

_________________
Mitch Hunt
GMAT Private Tutor and Instructor
GMATGuruNY@gmail.com
If you find one of my posts helpful, please take a moment to click on the "Thank" icon.
Contact me about long distance tutoring!

Last edited by GMATGuruNY on Wed Jun 13, 2012 7:09 am; edited 1 time in total

Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
hey_thr67 Really wants to Beat The GMAT!
Joined
15 Feb 2011
Posted:
299 messages
Followed by:
2 members
Thanked:
9 times
Wed Jun 13, 2012 7:07 am
I tried to attempt the Question using this approach but lets says food per dog has to be constant So,

(cans x days)/no. of dogs = k
So using this approach we have

(6x35)/10 = n x 12/7

and hence the answer is in fractions. Please let me know where am i getting wrong.

Ashujain Really wants to Beat The GMAT!
Joined
20 Apr 2012
Posted:
123 messages
Followed by:
1 members
Thanked:
28 times
Thu Jun 14, 2012 3:00 am
hey_thr67 wrote:
I tried to attempt the Question using this approach but lets says food per dog has to be constant So,

(cans x days)/no. of dogs = k
So using this approach we have

(6x35)/10 = n x 12/7

and hence the answer is in fractions. Please let me know where am i getting wrong.
@hey_thr67

You are multiplying 'cans of food' with the 'no. of the days'. It is wrong.
We have to divide the cans by no. of days and by no. of dogs that will give us the avg food consumption by 1 dog in 1 day.

Hope it helps!

### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
Joined
25 May 2010
Posted:
6092 messages
Followed by:
1039 members
Thanked:
5258 times
GMAT Score:
790
Thu Jun 14, 2012 5:17 am
hey_thr67 wrote:
I tried to attempt the Question using this approach but lets says food per dog has to be constant So,

(cans x days)/no. of dogs = k
So using this approach we have

(6x35)/10 = n x 12/7

and hence the answer is in fractions. Please let me know where am i getting wrong.
x/y = k implies the following: if x increases by a factor, then y increases by the same factor.

In my solution, (dogs*days)/cans = k.
This relationship holds true because:
If the number of dogs doubles, then the number of cans must double -- even if the number of days is unchanged.
If the number of days doubles, then the number of cans must double -- even if the number of dogs is unchanged.

In your solution, (cans * days)/no. of dogs = k.
This relationship is not valid: the number of days is NOT directly proportional to the number of dogs.
Quite the opposite.
If the number of cans remains constant, then, as the number of dogs INCREASES, the number of days must DECREASE.
TWICE AS MANY dogs can be fed for HALF the number of days.

_________________
Mitch Hunt
GMAT Private Tutor and Instructor
GMATGuruNY@gmail.com
If you find one of my posts helpful, please take a moment to click on the "Thank" icon.
Contact me about long distance tutoring!

Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

### Best Conversation Starters

1 varun289 40 topics
2 guerrero 21 topics
3 sana.noor 20 topics
4 killerdrummer 19 topics
5 sanaa.rizwan 14 topics
See More Top Beat The GMAT Members...

### Most Active Experts

1 Brent@GMATPrepNow

GMAT Prep Now Teacher

203 posts
2 GMATGuruNY

The Princeton Review Teacher

140 posts
3 Jim@StratusPrep

Stratus Prep

100 posts
4 Anju@Gurome

Gurome

99 posts