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after solving this problem I learnt two things:
1) Reading the question well enough tells us what to solve for and avoids taking longer routes.
2) If we adopt an accounting approach via something like a double matrix here, it will become more challenging to solve this problem.

The question gives info on Females and population older than 70 years, but asks about a probability of males or younger. Well some arithmetic and probability we need to do.

P(male or <70 yrs) = Prob(male)+Prob(<70)-Prob(male and <70).
let us compute our sample space
n(male) = 2500-850 = 2550-900=1650.
Notice that second part is really number of female and <70 yrs = > 2/5*850= 340.
n of event space = 1650+340 = 1990.
prob = n of event space / number of entire population = 1990/2500 =>199/250.
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Bunuel
In a village of 2,500 people, 800 people are over 70 years old and 850 people are female. It is known that 40 percent of the females are younger than 70 years old. If no one in the village is 70 years old, what is the probability that a person chosen at random is either a male or younger than 70 years old?

A. 221/250
B. 199/250
C. 33/50
D. 8/25
E. 51/250


2500 people

800 over 70

850 female

40% female younger than 70 = 850(0.4) = 340

850 - 340 = 510 greater than 70 for female

Males = 2500 - 850 = 1650

If 800 are greater than 70 and 510 females are greater than 70, then 800 - 510 = 290 males are greater than 70 years old.

1650 - 290 = 1360 males younger than 70

probability that a person chosen at random is either a male or younger than 70 years old:

(total males, which includes less than 70 years + females less than 70) = 1650 + 340 = 1990

1990/2500 = 199/250 B

or (males less than 70 + females less than 70 + males over 70) = 1360+340+290 = 1990

1990/2500 = 199/250 B
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Hello from the GMAT Club BumpBot!

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