Time and Work Practice Test 5 with solutions

Work done by them in one day = $\frac{1}{30}+\frac{1}{10}+\frac{1}{5}$
= $\frac{1+3+2}{30}$ = $\frac{6}{30}$ = $\frac{1}{5}$
Work done by them in 2 days = $\frac{2}{5}$
Work left = 1 - $\frac{2}{5}$ = $\frac{3}{5}$
Number of days taken by C alone to complete the work = 15 days
So, $\frac{3}{5}$ th of work will be completed in
= $15\times \frac{3}{5}$ = 9 days