P can work thrice as fast as Q working independently, can complete a task in 24 days. In how many days can P and Q together finish the same task?

Answer: Option C

\begin{array}{*{20}{c}} {}&{\text{P}}&{}&{\text{Q}} \\ {{\text{Efficiency}}}&3&:&1 \\ {{\text{Time}}}&1&:&3 \end{array}
3 unit → 24 days
1 unit → 8 days
Total work = 24
P + Q can complete the same work = $$\frac{24}{4}$$ = 6 days