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?

Let volume of cistern = L.C.M.(12,18,24) = 72 litres

A can fill the pipe in 12 minutes, => A's efficiency = $$\frac{72}{12}=6$$ litres/min

Similarly, B's efficiency = $$4$$ litres/min and C = $$3$$ litres/min

If all are opened for 7 minutes, cistern filled = $$(6+4+3)\times7=91$$ litres

=> Volume of the water that over flows as the percentage of the total volume of the cistern = $$\frac{(91-72)}{72}\times100$$

= $$\frac{1900}{72}=\frac{475}{18}=26\frac{7}{18}\%$$

=> Ans - (A)