Bunuel wrote:
Two pipes A and B can fill a tank in 8 hours. If only pipe A is open then it would take 4 hours longer to fill the tank. Find how much longer would it take if only pipe B is open.
A. 6 hours
B. 8 hours
C. 10 hours
D. 12 hours
E. 16 hours
solution:
rate of A+rate of B= total rate, and if the work done is one then we get the total time to finish.
1/A+1/B=1/Total
1/A+1/B=1/8. and given that rate of A=8+4=12 hours
so 1/12+1/B=1/8
1/B=1/8-1/12.. we get B as 24, now, how much longer tha 8 will it take then 24-8=16.
Option E.16 hours more