a can do a work in 20 days and b in 30 days . if they work on it together for 4 days , then the fraction of the work that is left is :
"ans is : b a ' s 1 day ' s work = 1 / 20 b ' s 1 day ' s work = 1 / 30 ( a + b ) ' s 1 day ' s work = ( 1 / 20 + 1 / 30 ) = 1 / 12 ( a + b ) ' s 4 day ' s work = ( 1 / 12 * 4 ) = 1 / 3 therefore , remaining work = ( 1 - 1 / 3 ) = 2 / 3"
subtract(const_1, multiply(add(divide(const_1, 20), divide(const_1, 30)), 4))