A man has a pool. This full pool can be drained using four different drainage, if he uses A it takes 10 hours to drain pool, if he uses B it takes 50 hour to drain and if he uses C it takes 5 hours to drain the pool. He first runs the water by A for 5 hours, then turning that off, he continues with B for 10 hours. Then turning that off as well he uses C for 1 hours and lastly using D for 1 hour the pool is empty. How long does it take to empty the pool only using the drainage D?  Choose the correct choice from the following answers
A) 2 hours  B) 4 hours  C) 6 hours  D) 8 hours  E) 10 hours
1 - (5/10 +10/50 +2/5 + 1/x) = 0 x = 10 hours ANSW10 hoursR = 10 hours
<result>E</result>
A man has a pool. This full pool can be drained using four different drainage, if he uses A it takes 10 hours to drain pool, if he uses B it takes 50 hour to drain and if he uses C it takes 5 hours to drain the pool. He first runs the water by A for 5 hours, then turning that off, he continues with B for 10 hours. Then turning that off as well he uses C for 1 hours and lastly using D for 1 hour the pool is empty. How long does it take to empty the pool only using the drainage D?