GMAT prep PS question

Lets have the Total number of students as T=1000
then M= 480 and F=520.

Now M and F who are > 25 yrs are
M= 480*40/100=192
F=520*1/5=104

Hence Probability,P=192/1000 + 104/1000 = 296/1000 = 0.296=0.3 approx

D.) = 0.3

- Deepak

are u sure???

100 students..

approx. 50 male 50 female

20 males 25+....10 females 25+

therefore...70 under 25...

therefore prob. of being selected is 70/100 = 0.70

correct me if i am wrong please...

I second for 0.7
40/100 of 48 male=19.2 greater than 25
20/100 of 52 female=10.4 greater than 25
19.2+10.4=29.6 greater than 25
So appr 70% is less than 25
And the probability is 70 out 100=0.7

Answer is .70, first solution is correct except for it is solved for the probability of someone greater than 25 and the question asks for less than 25.

For a quick way use a class size of 1000
M=480; M<25=480*.6=288
F=520; F<25=520*.8=416

M+F/1000=704/1000=.704

Normally using a value of 100 works well in percent questions but when you get decimals for values when you need integers (i.e. People) just move the decimal to the right one place.

Thanks Rossmj..The community Sponsors is actually partly covering the question and hence i missed the last part..thanks for correcting

-Deepak

let the class strength be 100
Males = 48
Females =52

now, 40% of M are 25+
so, 60% of M less than 25

thus, 0.6*48 = 28.8 males = 29 M

Similarly,
20% of 52 F are 25+
so, 80% of 52 F are less than 25 yrs

thus,
0.8*52 = 42 F less than 25

total people less than 25 = 29M+42 F = 71

total = 100
Prob = 71/100 = 0.71

Hope this Helps

Yea answer is D.

Best way to do this problem, in my opinion, is with a matrix.

answer is B .70