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by kartikshah » Fri Jul 27, 2012 6:00 pm
In a class of 50 students, 10 did not opt for math. 15 did not opt of science and 2 did not opt for either. How many students of the class opted for both math and science?

A. 37

B. 25

C. 23

D. 27

E. 48

I don't have the OA for this one too!! But my working showed D to be the right answer.
Is D correct?
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by Birottam Dutta » Fri Jul 27, 2012 6:12 pm
As 2 students did not opt for any class,

Number of students who opted for at least one class = 50-2 = 48.

let a be no of students who opted for only math.
let c be no of students who opted for only science.
let b be no of students who opted for both math and science.

as 10 did not opt for math, c=10.
as 15 did not opt for science, a=15.

Now, a+b+c = 48, => b = 48-(10+15) = 23.

Answer =C.

Hope this helps!
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by tisrar02 » Fri Jul 27, 2012 6:55 pm
I got D by making a Table.

Something like this

____________Math____________No Math ________Total
Science_____27_____________13_______________40

No Science____8_____________2 (given)__________10(given)

Total________35_____________15(given)_______________50


Sorry misread the question the first time. The Answer should be D
Last edited by tisrar02 on Sat Jul 28, 2012 5:13 pm, edited 1 time in total.
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by tutorphd » Fri Jul 27, 2012 8:34 pm
total = 50
neither = 2
no_math = 10 -> math=50-10=40 (including math_only and math_and_science)
no_science = 15 -> science = 50 - 15 = 35 (including science_only and math_and_science)

Use the formula:

total = math + science - both + neither
50 = 40 + 35 - both + 2

both = 27
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