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# Each student in a class is to choose an optional subject.

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Intern
Joined: 15 Sep 2017
Posts: 34
Followers: 0

Kudos [?]: 15 [0], given: 2

Each student in a class is to choose an optional subject. [#permalink]  12 Sep 2018, 22:35
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Question Stats:

99% (00:56) correct 0% (00:00) wrong based on 7 sessions
Each student in a class to choose an optional subject.If $$\frac{1}{5}$$ chose math,$$\frac{1}{4}$$chose biology,$$\frac{1}{2}$$ chose history and the remaining 10 chose psychology.what is the number of students in the class?

A) 80

B) 110

C) 160

D) 200

E) 400
[Reveal] Spoiler: OA
Director
Joined: 20 Apr 2016
Posts: 824
WE: Engineering (Energy and Utilities)
Followers: 10

Kudos [?]: 601 [1] , given: 121

Re: Each student in a class is to choose an optional subject. [#permalink]  13 Sep 2018, 19:34
1
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AchyuthReddy wrote:
Each student in a class to choose an optional subject.If $$\frac{1}{5}$$ chose math,$$\frac{1}{4}$$chose biology,$$\frac{1}{2}$$ chose history and the remaining 10 chose psychology.what is the number of students in the class?

A) 80

B) 110

C) 160

D) 200

E) 400

Let X be the total no.

so $$x-\frac{x}{5}-\frac{x}{4}-\frac{x}{2} = 10$$

or $$x(1-\frac{1}{5}-\frac{1}{4}-\frac{1}{2}) = 10$$

or $$x = 10 * 20 = 200$$

------------------------------------------------

Another way to solve ,

just use the number from the solution

it is always advisable to start with option C

So if the total no. = 160,

then $$(\frac{1}{5} * 160) + (\frac{1}{4} * 160) + (\frac{1}{2} * 160)$$ = not equal to 160

move to option D

if the total no is 200 then

then $$(\frac{1}{5}* 200) + (\frac{1}{4} * 200) + (\frac{1}{2} * 200) = 200$$and hence our answer
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Re: Each student in a class is to choose an optional subject.   [#permalink] 13 Sep 2018, 19:34
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# Each student in a class is to choose an optional subject.

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