A cistern has three pipes, A, B and C. The pipes A and B can fill it in 4 and 5 hours respectively and C can empty it in 2 hours. If the pipes are opened in order at 1,2 and 3 A. M. When will the cistern be empty?
A. 3 PM
B. 7 PM
C. 4 PM
D. 5 PM
Answer:D
A cistern has three pipes, A, B and C. The pipes A and B can fill it in 4 and 5 hours respectively and C can empty it in 2 hours. If the pipes are opened in order at 1,2 and 3 A. M. When will the cistern be empty?
A. 3 PM B. 7 PM C. 4 PM D. 5 PM