a rope of which a calf is tied is increased from 15 m to 18 m , how much additional grassy ground shall it graze ?
"π ( 182 – 152 ) = 311.14 answer : d"
multiply(subtract(power(18, const_2), power(15, const_2)), divide(add(multiply(15, const_2), const_2), add(const_4, const_3)))