A alone can do a piece of work in 12 days. B alone can do the same work in 18 days. C alone can do the same work in 24 days. In how many days will they complete 65% of the work, if all three work together?

3.6 days

A = 12 days, B = 18 days, C = 24 days,

⇒ 65% of total work = \(\frac{65}{100}\) x 72 = 46.8 units,

⇒ Time required for A + B + C to complete 65% of the work = \(\frac{46.8}{6+4+3}\) = \(\frac{46.8}{13}\) = 3.6 days,  ..(\(\frac{Work}{Efficiency}\) = Time)