$\begin {array} {1 1} (A)\;40 & \quad (B)\;20 \\ (C)\;80 & \quad (D)\;60 \end {array}$

Let the number of boys and girls be $x$ and $y$

$ \therefore 52x+42y=50(x+y)$

$ 52x+42y=50x+50y$

$ 52x-50x=50y-42y$

$ 2x=8y$

$ x = 4y$

Total number of students in the class = $ x+y$

$ = 4y+y$

$ = 5y$

Percentage of boys = $ \large\frac{4\not{y}}{\not{5}\not{y}} \times {\not100}^{20}$

$ = 80$

Ans : (C)

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