Delhi Police Constable Exam Model Paper 7

Given:
Percentage of invalid votes = 20%
Winner gets = 70% of valid votes Win by 9600 votes
Calculation:
Let the total number of voters be x
So, total number of valid votes = (80/100) x = 0.8 x
If the winner gets 70% of valid votes then the loser gets vote = 30% of valid votes
So according to question,
$70\%\mathit{o}\mathit{f}0.8\mathit{x}=30\%\mathit{o}\mathit{f}0.8\mathit{x}+9600$
⇒ $0.56\mathit{x}=0.24\mathit{x}+9600\Rightarrow 0.32\mathit{x}=9600$
⇒ $\mathit{x}=30000$
∴ Total number of votes = 30,000
Short trick:
Let the total votes be 100
So valid votes = 80
Winner gets $70\%$ of $80=56$
Loser gets $30\%$ of $80=24$
Difference = 32
So $32=9600$
⇒ 1 = 300
∴ Total votes $=100\times 300=30,000$