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

Original illiterate population = 150 lakhs

Decreased illiterate population = 100 lakhs

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

$\therefore$Percentage decrease in illiterate population = $\left(\frac{Decrease in illiterate population}{Original illiterate population}\right)\times 100$

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

= 33.33% decrease in illiterate population.