The number of illiterate people in a country decreased from 150 lakhs to 100 lakhs in 10 years. What is the percentage of decrease?

Initial illiterate population = 150 lakhs

New illiterate population = 100 lakhs

Decrease in illiterate population = 150 lakhs – 100 lakhs = 50 lakhs

∴ Percentage decrease in the illiterate population$=\left(\frac{\mathrm{Decrease} \mathrm{in} \mathrm{illiterate} \mathrm{population}}{\mathrm{Initial} \mathrm{illiterate} \mathrm{population}}\right)\times 100$

$=\left(\frac{50 \mathrm{lakhs}}{150 \mathrm{lakhs}}\right)\times 100$

$=33.33\%$

So the percentage decrease of illiterate population is 33.33%.