Question : A man alone can paint a house in 9 days and a woman alone can paint the house in 18 days. If 3 men and 3 women worked together, then in how many days they will paint the house?

Question : A alone can do a piece of work in 7 days, while B alone can do it in 10 days. In how many days will they complete the same work if they both work together?

Question : A alone can do a piece of work in 10 days. B alone can do the same work in 12 days. They work on alternate days starting with A. In how many days will they complete $\frac{3}{4}$th of the total work?

Question : A and B can do a piece of work in 8 days, B and C can do it in 24 days while C and A can do it in $8\frac{4}{7}$ days. In how many days can C do it alone?

Question : $\mathrm{N}_1$ alone can do 20% of a piece of work in 6 days, $\mathrm{N}_2$ alone can do 20% of the same work in 4 days, and $\mathrm{N}_3$ alone can do 50% of the same work in 12 days. In how many days can they complete the work, if all of them work together?