the population of a town is 20000 . it decreases annually at the rate of 20 % p . a . what will be its population after 2 years ?
"20000 × 80 / 100 × 80 / 100 = 12800 answer : e"
subtract(subtract(20000, multiply(20000, divide(20, const_100))), multiply(subtract(20000, multiply(20000, divide(20, const_100))), divide(20, const_100)))