Time and Work - Efficiency Model

1) A is thrice as good a workman as B and takes 10 days less to do a piece of work than B takes. the number of days taken by B to finish the work is:

a) 12                      b) 15                 c) 20                   d) 30

2) A does half as much work as B in 3/4 of the time. If together they take 18 days to complete the work, how many days will B take to do it?

a) 30                    b) 35                 c) 40                    d) 45

3) A works twice as fast as B. If B can complete a piece of work independently in 12 days, then the number of days taken by A and B together to finish the work is:

a) 4                        b) 6                 c) 8                          d) 18

4) A and B working separately can do a piece of work in 9 and 12 days respectively.If they work for a day alternately, A beginning, in how many days, the work will be completed?

a) 10 1/2            b) 10 1/4           c) 10 2/3             d) 10 1/3

5) A cistern has a leak which would empty it in 8 hours. A tap is turned on which admits 6 liters a minute into the cistern and it is now empited in 12 hours. how many litres does the cistern hold.

a) 7580              b) 7960             c) 8290              d) 8640

6) two pipes M and N can fill a cistern in 24 min and 32 min , repectively. If both the pipes are opened together, then after hoe many minutes N should be closed so that the tank is full in 18 minutes ?

a) 6                     b) 8                    c) 10                   d) 21x