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oil paintings

by Lattefah84 » Fri Jan 08, 2010 3:39 am
In a certain museum, 15 percent of the collection consists of oil paintings from the Impressionist period. If 40 percent of the oil paintings in the museum collection are not from the Impressionist period, what percent of the museum collection consists of oil paintings?

(A) 20%
(B) 25%
(C) 37.5%
(D) 62,5%
(E) 80%

I really don't understand this. if 15% + 40% are both oil paintings, shouldn't it be 55% of collection are oil paintings? Where's the trick?
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by Stuart@KaplanGMAT » Fri Jan 08, 2010 3:53 am
Lattefah84 wrote:In a certain museum, 15 percent of the collection consists of oil paintings from the Impressionist period. If 40 percent of the oil paintings in the museum collection are not from the Impressionist period, what percent of the museum collection consists of oil paintings?

(A) 20%
(B) 25%
(C) 37.5%
(D) 62,5%
(E) 80%

I really don't understand this. if 15% + 40% are both oil paintings, shouldn't it be 55% of collection are oil paintings? Where's the trick?
Hi!

We have to read this kind of question very carefully.

The first sentence tells us that 15% of the collection is impressionist oil paintings.

The second sentence tells us that 40% of the oil paintings are non-impressionist.

If 40% of the oil paintings are non-impressionist, then 60% of the oil paintings are impressionist.

Therefore, we know that 15%(total collection) = 60%(all oil paintings).

We want to know what percent of the collection is oil paintings, or in other words we want to solve for:

oil paintings/total collection.

15%(TC) = 60%(OP)
15%/60% = OP/TC
1/4 = OP/TC

and 1/4 = 25%, so choose (B).
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by Lattefah84 » Fri Jan 08, 2010 4:51 am
Stuart Kovinsky wrote:
Lattefah84 wrote:In a certain museum, 15 percent of the collection consists of oil paintings from the Impressionist period. If 40 percent of the oil paintings in the museum collection are not from the Impressionist period, what percent of the museum collection consists of oil paintings?

(A) 20%
(B) 25%
(C) 37.5%
(D) 62,5%
(E) 80%

I really don't understand this. if 15% + 40% are both oil paintings, shouldn't it be 55% of collection are oil paintings? Where's the trick?
Hi!

We have to read this kind of question very carefully.

The first sentence tells us that 15% of the collection is impressionist oil paintings.

The second sentence tells us that 40% of the oil paintings are non-impressionist.

If 40% of the oil paintings are non-impressionist, then 60% of the oil paintings are impressionist.

Therefore, we know that 15%(total collection) = 60%(all oil paintings).

We want to know what percent of the collection is oil paintings, or in other words we want to solve for:

oil paintings/total collection.

15%(TC) = 60%(OP)
15%/60% = OP/TC
1/4 = OP/TC

and 1/4 = 25%, so choose (B).

Thank You very much for the explanation, I got it now
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