how many times digit 20 is used while writing numbers from 100 to 500 ?
"in 100 to 200 there are 5 20 ' s in 200 to 300 there are 5 20 ' s in 300 to 400 there are 5 20 ' s in 400 to 500 there are 5 20 ' s so , total 20 is 20 ' s correct option : a"
add(add(divide(subtract(500, 100), const_10), multiply(add(const_10, const_1), add(const_10, const_1))), multiply(20, const_2))