A is 40% more efficient than B. If B alone can complete a work in 42 days, then A alone can complete the same work in how many days?
Let total work to be done = 42 units
B can complete the work in 42 days, => B's efficiency = $$\frac{42}{42}=1$$ unit/day
A is 40% more efficient than B, => A's efficiency = $$1+(\frac{40}{100}\times1)=1.4$$ units/day
$$\therefore$$ Time taken by A = $$\frac{42}{1.4}=30$$ days
=> Ans - (C)
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