cats and dogs

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nidhis.1408: Master | Next Rank: 500 Posts; Posts: 135; Joined: Mon Oct 03, 2011 6:54 amFollowed by: 4 members

by nidhis.1408 » Tue Nov 15, 2011 1:37 pm

A certain animal shelter has 28 cats and 46 dogs. how many dogs must be adopted and taken away from the animal shelter so that 70% of the animal in the shelter wil be cats?
a. 6
b. 12
c. 28
d. 34
e. 40

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shankar.ashwin: Legendary Member; Posts: 966; Joined: Sat Jan 02, 2010 8:06 amFollowed by: 21 members; Thanked: 230 times

by shankar.ashwin » Tue Nov 15, 2011 3:41 pm

28 cats becomes 70% means 100% is 28/0.7 = 40.

Therefore remaining (40-28) = 12 will be dogs. therefore 46-12 = 34 dogs should be taken away. D IMO

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gmatpup: Senior | Next Rank: 100 Posts; Posts: 88; Joined: Sat Oct 15, 2011 6:38 pmFollowed by: 1 member; Thanked: 1 times

by gmatpup » Wed Nov 16, 2011 8:08 am

You can also use the answer choices to help you out if you find this easier.

As of now we have 28 cats and 46 dogs. Add them together so our total is 74.

We have 28/74 cats = approx. 38%

Now, let's look at the answer choices. Start with any of them. I just happened to start with D (34).

First, subtract 34 from 46 = 12

Then we have to subtract the 34 from our total of course, so 74 - 34 = 40.

Now, let's see what percentage of cats we would have. 28/74 = 70%

I hope this helps

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Abhishek009: Master | Next Rank: 500 Posts; Posts: 359; Joined: Wed Mar 11, 2009 4:37 amFollowed by: 2 members; Location: Kolkata, India; Thanked: 50 times

by Abhishek009 » Wed Nov 16, 2011 8:54 am

nidhis.1408 wrote:A certain animal shelter has 28 cats and 46 dogs. how many dogs must be adopted and taken away from the animal shelter so that 70% of the animal in the shelter wil be cats?
a. 6
b. 12
c. 28
d. 34
e. 40

Total animals = 28+46 =>74

Let the no of dogs adopted be x

28/46 - x = 70/100

28/48-x = 7/10

280 = 336 - 7x

7x = 56

So x = 8 , hence 8 dogs must be adopted and taken away from the animal shelter....

Abhishek

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rbales: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Mon Oct 10, 2011 7:56 am

by rbales » Wed Nov 16, 2011 1:18 pm

Since we're calculating based on the number of dogs taken away, let's solve the problem for 70% of animals being dogs. Let x equal the number of dogs to be subtracted.

Code: Select all

 46-x     30
------ = ----
 74-x     100

Note: Be sure to subtract the number of dogs from the number of animals, since that number will represent the new number of total animals.

> 100(46-x) = 30(74-x)
> 4600 - 100x = 2220 - 30x
> 2380 = 70x
> x = 34

Answer:D, 34 dogs

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MBA.Aspirant: Master | Next Rank: 500 Posts; Posts: 401; Joined: Tue May 24, 2011 1:14 amFollowed by: 5 members; Thanked: 37 times

by MBA.Aspirant » Wed Nov 16, 2011 3:45 pm

nidhis.1408 wrote:A certain animal shelter has 28 cats and 46 dogs. how many dogs must be adopted and taken away from the animal shelter so that 70% of the animal in the shelter wil be cats?
a. 6
b. 12
c. 28
d. 34
e. 40

28/28+x = 70/100

2800 = 1960 +70x

x (no. of dogs now) = 12

number removed = 46 - 12 = 34

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Thu Dec 01, 2011 7:06 am

nidhis.1408 wrote:A certain animal shelter has 28 cats and 46 dogs. how many dogs must be adopted and taken away from the animal shelter so that 70% of the animal in the shelter wil be cats?
a. 6
b. 12
c. 28
d. 34
e. 40

The number of cats (28) does not change.
After the adoptions, the resulting ratio of cats to dogs = 70:30 = 7:3 = 28:12.
Since the number of dogs = 12, the number adopted = 46-12 = 34.

The correct answer is D.

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8137; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Tue May 08, 2018 10:37 am

nidhis.1408 wrote:A certain animal shelter has 28 cats and 46 dogs. how many dogs must be adopted and taken away from the animal shelter so that 70% of the animal in the shelter wil be cats?
a. 6
b. 12
c. 28
d. 34
e. 40

There are a total of 28 + 46 = 74 animals. Let d denote the number of dogs to be removed so that 70% of the remaining animals are cats. We can create the equation:

28/(74 - d) = 7/10

280 = 7(74 - d)

280 = 518- 7d

7d = 238

d = 34

Alternate solution:

If the cats are 70% of the animals in the shelter and since the number of cats is 28, then the total number of animals in the shelter can only be 28/0.7 = 280/7 = 40. Thus there can be only 40 - 28 = 12 dogs in the shelter. Since there are currently 46 dogs, 46 - 12 = 34 dogs should be removed.

Answer: D

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