If 12 men and 6 boys can do a work in 4 days and 4 men and 14 boys can do the same work in 8 days, find the ratio of efficiency of a man to that of a boy.
According to question,
$$\left(12m+6b\right)\times4=\left(4m+14b\right)\times8.$$
or,$$\left(12m+6b\right)=\left(4m+14b\right)\times2$$
or,$$12m+6b=8m+28b.$$
or,$$4m=22b.$$
or,$$\frac{m}{b}=\frac{22}{4}=\frac{11}{2}.$$
So, D is correct choice.
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