In a chemical plant, there are 5 pipelines A, B, C, D and E carrying pure water, 10% HCL, 20% HCL, 30% HCL and 40% HCL respectively. A, B, C, D and E can individually fill a cistern in 20, 30, 60, 90 and 120 hours respectively. On Monday morning at 10 am pipe A is opened. Thereafter at the end of every hour, the other pipes are opened in the order B, C, D and E. The concentration of HCL in the cistern at 6 pm on the same day will be?
a)7%
b)8.92%
c)9.8%
d)10.72

• pipes-> A B C D E
  water 10% 20% 30% 40%(hcl)
  time-> 20 30 60 90 120(hrs)
  now at 10am pipe A is opened upto 6pm=8hrs.It is only water.so, conc of hcl is 0.
  now at 11am pipe B is opened upto 6pm=7hrs becaz after every hour next pipe will be opened.In 30hrs B can fill cistern with 10% hcl but B is opened for only 7hrs.so,only 2.3333333%hcl is moved to cistern from B.
  now at 12pm pipe C is opened upto 6pm=6hrs.In 60hrs C can fill cistern with 20% hcl but C is opened for only 6hrs.so,only 2%hcl is moved to cistern from C.
  now at 01pm pipe D is opened upto 6pm=5hrs.In 90hrs D can fill cistern with 30% hcl but D is opened for only 5hrs.so,only 1.6666666667%hcl is moved to cistern from D.
  now at 02pm pipe E is opened upto 6pm=4hrs.In 120hrs B can fill cistern with 40% hcl but C is opened for only 4hrs.so,only 1.33333333%hcl is moved to cistern from E.
  
  now 0+2.3333333+2+1.6666666667+1.333333333 = 7.1%~7%
  
  answer is A=7%
• 7 years agoHelpfull: Yes(11) No(1)
• Answer: B
  Here are 5 pipes A, B, C, D, E
  If we calculate the Efficiency of each pipe
  Pipe Efficiency Total Work hrs. Total (Water+HCl) HCl (calc. From Concentrated)
  A 18 8 144 0.0 (0%)
  B 12 7 084 8.4 (10%)
  C 06 6 036 7.2 (20%)
  D 04 5 020 6.0 (30%)
  E 03 4 012 4.8 (40%)
  
  Overall HCl in cistern is 26.4 L
  
  Total % Concentration of HCl in Cistern is (26.4/296)*100 Which is = 8.918~ 8.92%
  
  Hence answer is B
• 7 years agoHelpfull: Yes(3) No(5)
• pipes-> A B C D E
  water 10% 20% 30% 40%(hcl)
  time-> 20 30 60 90 120(hrs)
  now at 10am pipe A is opened upto 6pm=8hrs.It is only water.so, conc of hcl is 0.
  now at 11am pipe B is opened upto 6pm=7hrs becaz after every hour next pipe will be opened.In 30hrs B can fill cistern with 10% hcl but B is opened for only 7hrs.so,only 2.3333333%hcl is moved to cistern from B.
  now at 12pm pipe C is opened upto 6pm=6hrs.In 60hrs C can fill cistern with 20% hcl but C is opened for only 6hrs.so,only 2%hcl is moved to cistern from C.
  now at 01pm pipe D is opened upto 6pm=5hrs.In 90hrs D can fill cistern with 30% hcl but D is opened for only 5hrs.so,only 1.6666666667%hcl is moved to cistern from D.
  now at 02pm pipe E is opened upto 6pm=4hrs.In 120hrs B can fill cistern with 40% hcl but C is opened for only 4hrs.so,only 1.33333333%hcl is moved to cistern from E.
  
  now 0+2.3333333+2+1.6666666667+1.333333333 = 7.1%~7%
  
  answer is A=7%
• 7 years agoHelpfull: Yes(1) No(0)
• please any one solved me answer
• 7 years agoHelpfull: Yes(0) No(0)
• Answer is 10.73
• 6 years agoHelpfull: Yes(0) No(0)