In the graduating class of a certain college, 48 percent of

Since the numbers are in % form,let’s assume that the total base size of students is 100


Arranging them into table form,as calculation will be easier

Male Female Total
< 25 years old
29 42 71


>= 25 years old
(40/100)*48 = 19 (20/100)*52 =10 29


Total
48 52 100



Probability = Favourable possibilities/Total possibilities

= (29+42)/100

= (71)/100 = 0.71

We can let the total students = 1000.

Thus, there are 480 male students and 520 female students.

Since 60 percent of the male students are less than 25 years old, 0.6 x 480 = 288 are less than 25 years old.

Since 80 percent of the female students are less than 25 years old, 0.8 x 520 = 416 are less than 25 years old.

Thus, there are 288 + 416 = 704, rounded to 700, people who are less than 25 years old. Therefore, the probability that a randomly selected person is less than 25 years old is approximately 700/1000 = 0.7.

Answer: B

Method 1:

In such types of questions a flowchart is helpful in understanding the data which is required to get the solution

Let the total number of students be 1000

Referring to the flowchart, the total number of students \(\geq 25\) years of age = 192 + 104 = 296

The number of students < 25 years of age = 1000 - 296 = 704


Therefore the required probability = \(\frac{704 }{ 1000}\) = 0.704 \(\approx\) 0.7


Method 2:

Since the answer options are not at all close to each other, we can use a simple approximation method.

48% is \(\approx\) 50% and 52% is also \(\approx\) 50%

60% of males and 80% of females are less than 25 years old

Therefore (0.5 * 0.6) + (0.5 * 0.8) = 0.3 + 0.4 = 0.7


Option B

Arun Kumar

Bumping for review and further discussion*. Get a kudos point for an alternative solution!

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Shocked this is an actual gmat question. The percentages don't give interger values for those 25+. Had it not been for the "approximatly" I would have just thrown my hands in resignation. Still such an odd questions.

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total x
male = 0.48x
female = 0.52x

In this class 40 percent of the male and 20 percent of the female students are 25 years old or older.
I infer this as 0.40 of x & not of 0.48x & 0.20 of x & not of 0.52x
as it says
In this class

Let the total number of students be 100.
Males = 48% = 48
Females = 52% = 52

40% Male and 20 % Female are ≥ 25 years.

=> \(\frac{40}{100}\) * 48 + \(\frac{20}{100}\) * 52 ≥ 25 years

=> 29.6 (approx 30) ≥ 25 years.

Therefore, under 25 years will be 100 - 29. 6 = 70.4 (approx 70)

Probability: \(\frac{Desired result }{ Total outcome}\)
Probability: \(\frac{70 }{ 100}\)

= 0.7

Answer B

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