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

Question

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

A. 0.9
B. 0.7
C. 0.45
D. 0.3
E. 0.25

Bunuel · Accepted Answer

Percent of students who are 25 years old or older is 0.4*48+0.2*52=~30, so percent of people who are less than 25 years old is 100-30=70.

Answer: B.

This can also be done with an approximation method. Since percent of men and women are almost the same (48% and 52%) then percent of students who are 25 years old or older will be close to the average of 40% and 20%, so close to 30%, which makes percent of people who are less than 25 years old close to 70%.

Answer: B.

lchen · Answer

I like to make diagrams. For me, it is easy to see clear steps this way

Attachment:

Class under 25.jpg [ 27.08 KiB | Viewed 56381 times ]

Step 1: Fill in what you know. 48% male, 52% female
Step 2: Do known calculations: 48% x 40% = 19.2%. 52% x 20% = 10.4%
Step 3: Fill in the rest of the chart as necessary. In this case, you just need the total 25 and older (19.2% + 10.4% = 29.6%) and under 25 (100-29.6%).
Step 4: Find the answer. The % under 25 is 70.4% which is approximately 70%

Answer is B

Bunuel · Answer

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shivanigs · Answer

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

alphabeta1234 · Answer

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.

Posted from my mobile device

Posted from my mobile device

paidlukkha · Answer

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

JeffTargetTestPrep · Answer

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

MathRevolution · Answer

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

CrackverbalGMAT · Answer

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

bumpbot · Answer

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