how many times digit 7 is used while writing numbers from 1 to 300 ?
"in 1 to 100 their are 14 seven ' s in 100 to 200 their are 14 seven ' s in 200 to 300 their are 14 seven ' s so total answer is 42 seven ' s correct option : b"
add(add(divide(subtract(300, 1), const_10), multiply(add(const_10, const_1), add(const_10, const_1))), multiply(7, const_2))