working at a constant rate , p can finish a job in 3 hours . q , also working at a constant rate , can finish the same job in 15 hours . if they work together for 2 hours , how many more minutes will it take p to finish the job , working alone at his constant rate ?
each hour they complete 1 / 3 + 1 / 15 = 2 / 5 of the job . in 2 hours , they complete 2 ( 2 / 5 ) = 4 / 5 of the job . the time for p to finish is ( 1 / 5 ) / ( 1 / 3 ) = ( 3 / 5 ) hour = 36 minutes the answer is b .
multiply(divide(subtract(const_1, multiply(add(inverse(3), inverse(15)), const_2)), inverse(3)), const_60)