BTGmoderatorDC wrote:In the graduating class of a certain college, 48 percent of the students are male and 52 percent are female. In this class 40 percent of the male and 20 percent of the female students are 25 years old or older. If one student in the class is randomly selected, approximately what is the probability that he or she will be less than 25 years old?
A. 0.9
B. 0.7
C. 0.45
D. 0.3
E. 0.25
Every student is EITHER male OR female.
Every student is EITER older OR younger.
For an EITHER/OR problem, use a DOUBLE MATRIX to organize the data:
_______________M______F_______Total
older:
younger:
total:
Let total students = 100:
_______________M______F_______Total
older:
younger:
total:__________________________100
48% males, 52% females.
Since we're looking for an approximation, let's say that 50% are males and 50% are females:
_________________M______F_______Total
older:
younger:
total:__________50_____50________100
40% of the males and 20% of the females are 25 and older:
_________________M______F_______Total
older:__________20_____10_______
younger:
total:__________50_____50________100
Complete the matrix:
_________________M______F_______Total
older:__________20_____10________30
younger:_______30_____40________70
total:__________50_____50________100
P(younger) = 70/100 = 0.7.
The correct answer is
B.
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