Management Aptitude Test Dec 2012 Paper

(d) Work done by A in 1 h = Work done by A, B and C in 1 h- Work done by B and C in 1 h
= $\frac{3}{8}-\frac{1}{4}=\frac{1}{8}$
∴ Work done by A and B in 1 h = $\frac{1}{8}+\frac{1}{6}=\frac{7}{24}$
Hence, A and B can complete the piece of work in $\frac{24}{7}$ i.e., in 3$\frac{3}{7}$ h