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?

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 : P and Q together can do a job in 6 days. Q and R can finish the same job in $\frac{60}{7}$ days. P started the work and worked for 3 days. Q and R continued for 6 days. Then the difference in days in which R and P can complete the job is:

Question : P and Q together can complete a piece of work in 6 days. If P can alone complete the work in 18 days, the number of days required for Q to finish the work is:

Question : A can complete $\frac{1}{3}$rd of a task in 7 days and B can complete $\frac{2}{7}$th of the same task in 10 days. In how many days can A and B together complete the task?