each boy contributed rupees equal to the number of girls and each..., Simplification, General Mathematics

Question:Each boy contributed rupees equal to the number of girls and each girl contributed rupees equal to the number of boys in a class of `60`students .If the total contribution thus collected is Rs `1600`,how many boys are there in the class ?

A `30` 
B `25` 
C `50` 
D Data inadequate

/94

+ AnswerD

+ ExplanationLet the number of boys `= x`

Then,number of girls`= (60 - x)`.

:.`x(60 - x) + (60 - x) x = 1600`

or `60x - x^2 + 60x - x^2 = 1600`

or `2x^2 - 120x + 1600 = 0`

or `x^2 - 60x + 800 = 0`

or `(x - 40)(x - 20)=0`

:.`x = 40`

or `20`

So,we are not definite .Hence data is inadequate.

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