NIFT PG 2019 Question Paper with solutions

Given, number of blue balls $=100$
Number of red balls $=50$
Number of black balls $=50$
According to the question,
Reduction in blue balls $=25\%$
Remaining balls $=100\times \frac{75}{100}$
Blue balls $=75$
Now, reduction in red balls $=50\%$
Similarly, number of remaining red balls $=25$
Total remaining balls $=75+25+50=150$
Percentage of black balls $=\frac{50\times 100}{150}$
$=\frac{100}{3}=33\frac{1}{3}\%$