To do a certain work, the ratio of efficiency of A to that of B is 3 : 7. Working together, they can complete the work in $$10\frac{1}{2}$$ days. They work together for 8 days. 60% of the remaining work will be completed by A alone in:

Solution (By Examveda Team)

\[\begin{array}{*{20}{c}} {}&A&{}&B \\ {{\text{Efficiency}} \to }&3&:&7 \end{array}\]
$$\eqalign{ & {\text{Total work}} = \left( {3 + 7} \right) \times \frac{{21}}{2} = 105 \cr & \left( {A + B} \right) \times 8 = \left( {3 + 7} \right) \times 8 = 80 \cr & {\text{Remaining work}} = 105 - 80 = 25 \cr & 60\% {\text{ work done by }}A = \frac{{25 \times 60}}{{100 \times 3}} = 5{\text{ days}} \cr} $$