Q27. 
Jay and Anup can do a job, each working alone in 30 and 15 days respectively. Jay started the work and after a few days, Anup joined him. They completed the work in 18 days from the start. After how many days did Anup join A? 
A.  6 

B.  10 

C.  12 

D.  14 
Q28. 
Pipe $A$ can fill a tank in '$a$' hours. On account of a leak at the bottom of the tank it takes thrice as long to fill the tank. How long will the leak at the bottom of the tank take to empty a full tank, when pipe $A$ is kept closed? 
A.  \(\dfrac{3a}{2}\) hours 

B.  \(\dfrac{2a}{3}\) hours 

C.  \(\dfrac{4a}{3}\) hours 

D.  \(\dfrac{3a}{4}\) hours 
Q29. 
Pavan builds an overhead tank in his house, which has three taps attached to it. While the first tap can fill the tank in 12 hours, the second one takes one and a half times than the first one to fill it completely. A third tap is attached to the tank which empties it in 36 hours. Now one day, in order to fill the tank, Pavan opens the first tap and after two hours opens the second tap as well. However, at the end of the sixth hour, he realizes that the third tap has been kept open right from the beginning and promptly closes it. What will be the total time required to fill the tank? 
A.  8 hours 48 minutes 

B.  9 hours 12 minutes 

C.  9 hours 36 minutes 

D.  8 hours 30 minutes 