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In the city of San Durango, 60 people own cats, dogs, or rab [#permalink]
02 Dec 2012, 00:45

1

This post received KUDOS

2

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

25% (medium)

Question Stats:

66% (01:53) correct
34% (01:19) wrong based on 111 sessions

In the city of San Durango, 60 people own cats, dogs, or rabbits. If 30 people owned cats, 40 owned dogs, 10 owned rabbits, and 12 owned exactly two of the three types of pet, how many people owned all three?

Re: In the city of San Durango, 60 people own cats, dogs, or rab [#permalink]
02 Dec 2012, 01:08

apoorvarora wrote:

In the city of San Durango, 60 people own cats, dogs, or rabbits. If 30 people owned cats, 40 owned dogs, 10 owned rabbits, and 12 owned exactly two of the three types of pet, how many people owned all three?

A 2 B 4 C 8 D 12 E 32

Total = C + D + R - (CD + DR + CR) - 2CDR

60 = 30 + 40 + 10 - (12) - 2x

x = 4

So, answer will be B Hope it helps! _________________

Re: In the city of San Durango, 60 people own cats, dogs, or rab [#permalink]
02 Dec 2012, 03:12

Expert's post

apoorvarora wrote:

In the city of San Durango, 60 people own cats, dogs, or rabbits. If 30 people owned cats, 40 owned dogs, 10 owned rabbits, and 12 owned exactly two of the three types of pet, how many people owned all three?

Re: In the city of San Durango, 60 people own cats, dogs, or rab [#permalink]
09 Dec 2012, 09:19

1

This post received KUDOS

Expert's post

@apoorvarora

when a problem is like you posted here or similar, like this one

Quote:

Each of the 59 members in a high school class is required to sign up for a minimum of one and a maximum of three academic clubs. The three clubs to choose from are the poetry club, the history club, and the writing club. A total of 22 students sign up for the poetry club, 27 students for the history club, and 28 students for the writing club. If 6 students sign up for exactly two clubs, how many students sign up for all three clubs?

is much better to use the formula Total = C + D + R - Exactly two - 2*All three (refers also to the post linked by Bunuel (the second one)

IF the problem is like this

Quote:

Workers are grouped by their areas of expertise, and are placed on at least one team. 20 are on the marketing team, 30 are on the Sales team, and 40 are on the Vision team. 5 workers are on both the Marketing and Sales teams, 6 workers are on both the Sales and Vision teams, 9 workers are on both the Marketing and Vision teams, and 4 workers are on all three teams. How many workers are there in total?

or this

Quote:

The 38 movies in the video store fall into the following three categories: 10 action, 20 drama, and 18 comedy. However, some movies are classified under more than one category: 5 are both action and drama, 3 are both action and comedy, and 4 are both drama and comedy. How many action-drama-comedy movies are there?

(souce MGMAT)

you can use either venn diagram or the formula Total= A+B+C - (AnB+AnC+BnC) +AnBnC + Neither is the same thing: it depends on which you are more comfortable

In the first case, that is the case of the question of the post at stake, is much better use the formula because is faster ans because set up a Venn diagram is more convoluted and prone of errors. Try to stay flexible.

Re: In the city of San Durango, 60 people own cats, dogs, or rab [#permalink]
16 Nov 2013, 07:38

MacFauz wrote:

Total = C + D + R - Exactly two - 2*All three

60 = 30 + 40 + 10 - 12 - 2x

2x = 8

x = 4

Why is the total number of "exactly two" that we are subtracting only 12? Why is it not 36? For each pair of groups we have one overlap... So for 3 pairs of groups, we should have 3*12 = 36... No?

Re: In the city of San Durango, 60 people own cats, dogs, or rab [#permalink]
16 Nov 2013, 07:44

Expert's post

ronr34 wrote:

MacFauz wrote:

Total = C + D + R - Exactly two - 2*All three

60 = 30 + 40 + 10 - 12 - 2x

2x = 8

x = 4

Why is the total number of "exactly two" that we are subtracting only 12? Why is it not 36? For each pair of groups we have one overlap... So for 3 pairs of groups, we should have 3*12 = 36... No?

In the city of San Durango, 60 people own cats, dogs, or [#permalink]
17 Jan 2014, 06:46

In the city of San Durango, 60 people own cats, dogs, or rabbits. If 30 people owned cats, 40 owned dogs, 10 owned rabbits, and 12 owned exactly two of the three types of pet, how many people owned all three?