Three pipes, A, B and C, can fill a cistern in 12, 18 and 24 minutes, respectively.If all the pipes are opened together for 7 minutes, what will be the volumeof the water that over flows as the percentage of the total volume of the cistern?

$26\frac{7}{18}$

A+ = 12 min, B+ = 18 min, C+ = 24 min,

⇒ A + B + C was opened for 7 min = (6 + 4 + 3) x 7 = 13 x 7 = 91 units,

⇒ Percentage of water overflowed = \(\frac{91-72}{72}\) x 100 = \( {26 }_{72 }^{28 } \) = \( {26 }_{18 }^{7 } \)