Question : A and B can complete a piece of work in 13 and 17 days respectively. A begins to do the work, and they work alternatively one at a time for one day each. The whole work will be completed in:

Question : P, Q, and R can complete a piece of work in 10 days, 15 days, and 20 days, respectively. If they work together, in how many days can they finish the same work?

Question : A and B can do a piece of work in 18 days, B and C in 24 days and A and C in 36 days. Working together, they can do the work in:

Question : To do a certain work, the ratio of the efficiencies of A and B is 7 : 5. Working together, they can complete the same work in $17 \frac{1}{2}$ days. A alone will complete 60% of the same work in:

Question : P and Q together complete a job in $4 \frac{2}{5}$ days. R and S complete the same job in $4 \frac{8}{9}$ days. If P, Q, R, and S work together, how many days do they need to complete the same job?