A city of 25,00,000 people has 3,750 licensed street vendors. The licensed vendors are what per cent of the city's people?

3750/2500000 = 0.0015, and multiplying by 100 gives 0.15%. A quick check keeps the decimal honest: 1% of 25,00,000 is 25,000, and 3,750 is well under a fifth of that, so the answer must be a fraction of one per cent. 1.5% would mean 37,500 vendors and 15% would mean 3,75,000 - both far too many. 0.015% would mean only 375. Each wrong option is one decimal place adrift.