A, B and C can complete a piece of work in 24, 6 and 12 days respectively. Working together, they will complete the same work in:
$ \dfrac{1}{24} $day
$ \dfrac{7}{24} $day
3$ \dfrac{3}{7} $days
4 days
Explanation:
$\left(A + B + C\right)$s 1 days work =$ \left(\dfrac{1}{24} +\dfrac{1}{6} +\dfrac{1}{12} \right) $=$ \dfrac{7}{24} $.
So, all the three together will complete the job in$ \left(\dfrac{24}{7} \right) $ days=3$ \dfrac{3}{7} $days.