Answer:
Option C
Explanation:
Let the total no. of voters be $= x$
No of voters polled $= 80$% of $x = \frac{4x}{5}$
Invalid votes $= 10$% of $\frac{4x}{5}$ $= \left(\frac{10}{100}\right)\times \left(\frac{4x}{5}\right)$
$ = \frac{2x}{25}$
Valid votes $= \left(\frac{4x}{5}\right)-\left(\frac{2x}{25}\right)$ $=\frac{18x}{25}$
Votes received by $A = 50$% of $\frac{4x}{5}$ $=\left(\frac{50}{100}\right)\times \left(\frac{4x}{5}\right)$
$= \frac{2x}{5}$
Votes received by $B = \left(\frac{18x}{25}\right)-\left(\frac{2x}{5}\right)$ $=\frac{8x}{25}$
Given, $\left(\frac{2x}{5}\right)-\left(\frac{8x}{25}\right) = 600$
$\therefore$ $\frac{2x}{25}= 600$
$\therefore$ $x = \frac{(600\times 25)}{2}$
$= 7500$