A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?  Pick.
A) 1/5 B) 29/35 C) 5/6 D) 35/29 E) 35/12
A needs 5 hours to complete the job   2A need 5/2 hours to complete the job,   similarly 3B need 7/3 hours to complete the job   Lets consider 2A and 3B as single entity (X, Y)   so   1/X + 1/Y = 1/Z Z is the time to complete the job if working together.   1/(2/5) + 1/(7/3) =1/Z   2/5 + 3/7 =1/Z   29/35 = 1/Z   Z = 35/29   so if 2A and 3 B working together, they would need 35/29 hours to complete the job.   ANSWER:35/29
<result>D</result>
A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?