Question

14. A and B working'separately can do a piece of work in
9 days and 15 days respectively. If they work for a
day alternately, with A beginning, then the work will
be completed in
(a) 10 days
(b) 11 days
(c) 9 days
(d) 12 days
​

Answer 1

Answer:

The answer is 9 days

Step-by-step explanation:

1/9+1/15

5+3/45= 8/45

8/45 - 1/15

8-3/45 = 5/45

=9days

Answer 2

Answer:

11 days

Step-by-step explanation:

A can do a piece of work in 9 days

B can do a piece of work in 15 days

Now, take the LCM of the days (9 and 15) and that is 45 and this is the whole work.

Now, find the efficiency of A and B by dividing the whole work by days individually of A and B and that will be:

45/9 = 5 (efficiency of A)

45/15 = 3 (efficiency of B)

Now, if they work alternatively according to the question then in the first day, work done by A will be 5 and in the second day the work done by B will be 3.

That means, In two days the work done will be 8

2 days = 8 work.....(i)

10 days = 40 work (by multiplying 5 in i)

and now, on next day A will come and complete the work by doing 5 work

Hence, In 11 days the work will be completed.