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# Among a group of 2,500 people, 35 percent invest in

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Manager
Joined: 11 May 2018
Posts: 125
Location: India
GMAT 1: 460 Q42 V14
Re: Among a group of 2,500 people, 35 percent invest in  [#permalink]

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09 Sep 2018, 03:20
1
dave13 wrote:
Bunuel wrote:
SOLUTION

Among a group of 2,500 people, 35 percent invest in municipal bonds, 18 percent invest in oil stocks, and 7 percent invest in both municipal bonds and oil stocks. If 1 person is to be randomly selected from the 2,500 people, what is the probability that the person selected will be one who invests in municipal bonds but NOT in oil stocks?

(A) 9/50
(B) 7/25
(C) 7/20
(D) 21/50
(E) 27/50

Given:
$$0.35*2,500=875$$ invest in municipal bonds;
$$0.07*2,500=175$$ invest in in both municipal bonds and oil stocks;

Therefore $$875-175=700$$ invest in municipal bonds but NOT in in oil stocks. (Or directly: 35%-7%=28% of 2,500, which is 700, invest in municipal bonds but NOT in in oil stocks).

$$P=\frac{Favorable}{Total}=\frac{700}{2,500}=\frac{7}{25}$$.

Bunuel is there a shortcut to calculate percent when it comes to big numbers. Quote time consuming....

$$0.35*2,500=875$$ invest in municipal bonds;
$$0.07*2,500=175$$ invest in in both municipal bonds and oil stocks;

Hi , as the question asked for the probability you can think that it will be fractions so we don't actually need to deal with numbers.
Only calculating percentages is sufficient.{checkout ENGRTOMBA2018 's answer regarding this.It is much more simple and takes less time to solve }
Hope it helps.
Intern
Joined: 11 Sep 2019
Posts: 6
Re: Among a group of 2,500 people, 35 percent invest in  [#permalink]

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14 Oct 2019, 05:37
Do we need to use 2500?, all are in % terms, gives the same result with 28/100 too
Re: Among a group of 2,500 people, 35 percent invest in   [#permalink] 14 Oct 2019, 05:37

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