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Answer is A

Let the number of persons be x

$\frac{6500}{x}=\frac{6500}{x+15}+30$

$\frac{6500}{x}-\frac{6500}{x+15}=30$

$6500 *(\frac{1}{x}-\frac{1}{x+15})=30$$6500 *\frac{x+15-x}{x(x+15)}=30$

$x^{2}+15x-3250=0$

Roots of the equation $ax^2 + bx +c = 0$ are given by $\dfrac{-b\pm \sqrt{b^2-4ac}}{2a}.$

So, we get $ x = \dfrac{-15 \pm \sqrt{225 +13000}}{2} = \dfrac{-15 \pm 115}{2} =50, -65$

Number of persons cannot be negative. So, x = **50**