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One person is to be selected at random from a group of 25 people. The probability that the selected person will be a male is 0.44, and the probability that the selected person will be a male who was born before 1960 is 0.28.

Quantity A = The number of males in the group who were born in 1960 or later
Quantity B = 4

A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.

The answer is C. How?

I understand that there are 11 males(.44*25)
How to find out how many males are there born before 1960?

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The answer is given "[...] and the probability that the selected person will be a male who was born before 1960 is 0.28.". So, there are $25*0.28 = 7$ males born before $1960$, so $11-7=4$ is the answer you're looking for.

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  • $\begingroup$ ah thanks, I was doing (.28 * 11) to find out the males born before 1960 $\endgroup$ – New to Rails Aug 15 '14 at 8:07
  • $\begingroup$ @New You're welcome. $\endgroup$ – Stefan Mesken Aug 15 '14 at 8:08
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$A=25\times P[\text {male and in or after 1960}]=25\times (P[\text{male}]-P[\text{male and born before 1960}])$

resulting in:

$A=25\times [0.44-0.28]=4$.

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