To do a certain work, the ratio of the efficiencies of A and B is 7 : 5. Working together, they can complete the same work in $$17\frac{1}{2}$$ days. A alone will complete 60% of the same work in:

Solution (By Examveda Team)

\[\begin{array}{*{20}{c}} {}&{\text{A}}&:&{\text{B}} \\ {{\text{Efficiency}}}&7&:&5 \end{array}\]
$$\eqalign{ & {\text{A}} + {\text{B}} = 12 \times \frac{{35}}{2} = 35 \times 6{\text{ Total work}} \cr & {\text{A}} = \frac{{35 \times 6 \times \frac{3}{5}}}{7} = 18{\text{ days}} \cr} $$