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collection of tough problems from G PREP - 8

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collection of tough problems from G PREP - 8

by abhasjha » Sat Feb 06, 2010 5:24 am
In a certain senior class, 72 percent of the male students and 80 percent of the female students have applied to college. What fraction of the students in the senior class are male?

(1) There are 840 students in the senior class

(2) 75 percent of the students in the senior class have applied to college
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Source: — Data Sufficiency |
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by linkinpark » Sat Feb 06, 2010 5:48 am
My pick is B

from 1 we don't know what % of actual students applied for college

from 2)

let x and y be male and female students respectively and total be n

so x + y = n (eqn a)

now from given info and stmt 2, 72% of x and 80% of y applied for class

so .72x + .80y = .75 of total i.e. n so .72x + .8y = .75n (eqn b)


eqn b can be multiplied by 100 and eqn a by 72 to solve them

72x + 80y = 75n
72x + 72y = 72n (-) subtract them

you'll get 8y = 3n
female student % = y = 3/8n * 100 , 100 - y will give male student %

hence B alone is sufficient.
530->480->580
when posting a question don't post OA(even masked) before some discussion.
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by onedayi'll » Sun Feb 07, 2010 8:55 pm
Agreed B alone is sufficient
Gym/GMAT/Girl -- Be Serious
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by abhasjha » Mon Feb 08, 2010 12:16 am
OA is B

Use method of alligation .......

males ------------- females

72 ------------------ -- 80


----- 75 --------------------------

5 ---------------------- 3


so the composition of the senior class is 5 males and 3 females .........
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