A and B together can finish a work in 20 days. If they worked together for 8 days, then what was the share of work that was yet to be completed?

A and B together can finish a work in 20 days. If they worked together for 8 days.

Then, together they need to work (20-8) = 12 days more to complete the work.

Share of work that was yet to be completed = $$\frac{12}{20}$$

= $$\frac{3}{5}$$

Another method

Let's assume the total work is 20 units.

A and B together can finish a work in 20 days.

The efficiency of A and B together = $$\frac{20}{20}$$ =  1unit/day

If they worked together for 8 days.

Work done by them in 8 days = $$8\times1$$ = 8 units

Remaining work = 20-8 = 12 units

Share of work that was yet to be completed = $$\frac{12}{20}$$

= $$\frac{3}{5}$$