working at a constant rate , p can finish a job in 4 hours . q , also working at a constant rate , can finish the same job in 15 hours . if they work together for 3 hours , how many more minutes will it take p to finish the job , working alone at his constant rate ?
"each hour they complete 1 / 4 + 1 / 15 = 19 / 60 of the job . in 3 hours , they complete 3 ( 19 / 60 ) = 19 / 20 of the job . the time for p to finish is ( 1 / 20 ) / ( 1 / 4 ) = ( 1 / 5 ) hour = 12 minutes the answer is d ."
multiply(divide(subtract(const_1, multiply(add(inverse(4), inverse(15)), 3)), inverse(4)), const_60)