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Of the 75 houses in a certain community, 48 have a patio. [#permalink]
21 Feb 2008, 12:37

3

This post received KUDOS

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A

B

C

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Difficulty:

45% (medium)

Question Stats:

36% (01:59) correct
63% (00:54) wrong based on 96 sessions

Of the 75 houses in a certain community, 48 have a patio. How many of the houses in the community have a swimming pool?

(1) 38 of the houses in the community have a patio but do not have a swimming pool. (2) The number of houses in the community that have a patio and a swimming pool is equal to the number of houses in the community that have neither a swimming pool nor a patio.

Re: GMATprep - Matrix [#permalink]
26 Feb 2008, 06:27

1

This post received KUDOS

bmwhype2 wrote:

Of the 75 houses in a certain community, 48 have a patio. How many of the houses in the community have a swimming pool?

(1) 38 of the houses in the community have a patio but do not have a swimming pool. (2) The number of houses in the community that have a patio and a swimming pool is equal to the number of houses in the community that have neither a swimming pool nor a patio.

finally can got my computer log in for work... so I can participate on GClub when I have nuffin to do.

Tricky problem. This is why its important to write everything out and not do it in your head.

youl notice we want x+z, which = m.

notice carefully that x+z also =27... its that simple, but so easy to miss... I missed it and said C at first.

Re: GMATprep - Matrix [#permalink]
26 Feb 2008, 13:14

GMATBLACKBELT wrote:

bmwhype2 wrote:

Of the 75 houses in a certain community, 48 have a patio. How many of the houses in the community have a swimming pool?

(1) 38 of the houses in the community have a patio but do not have a swimming pool. (2) The number of houses in the community that have a patio and a swimming pool is equal to the number of houses in the community that have neither a swimming pool nor a patio.

finally can got my computer log in for work... so I can participate on GClub when I have nuffin to do.

Tricky problem. This is why its important to write everything out and not do it in your head.

youl notice we want x+z, which = m.

notice carefully that x+z also =27... its that simple, but so easy to miss... I missed it and said C at first.

B

hmmm very tricky. we dont even need to know what z is. just M...
_________________

You tried your best and you failed miserably. The lesson is 'never try'. -Homer Simpson

Re: GMATprep - Matrix [#permalink]
31 Dec 2009, 09:19

6

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Here is my standard approach to solve such problems P= # of houses with patio only. Q= # of houses with pool only. R= # of houses with patio & pool. S= # of houses with no patio & no pool.

Given P+Q+R+S=75 & P+R=48 What is Q+R? (1)

Solving the first two equations Q+S+48=75 Q+S=27 (2)

Now let's look at the statements Statement 1 P=38 unnecessary and insufficient.

Statement 2 R=S Substituting in (1) Q+S? We know form (2) that Q+S=27 hence sufficient.
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Re: Of the 75 houses in a certain community, 48 have a patio. [#permalink]
09 Jan 2014, 03:49

We have a universal formula: Total= A + B - Both(A&B) + Neither

(1) is obviously insufficient.

(2) is sufficient because from the given conditions we get this: Both(A&B) = Neither = T(Let it be T, to make it simple) => 75 = 48 + B - T + T => B = 27.

The best answer is B!

gmatclubot

Re: Of the 75 houses in a certain community, 48 have a patio.
[#permalink]
09 Jan 2014, 03:49