A piece of work was finished by A, B and C together. A and B together finished 60% of the work and B and C together finished 70% of the work. Who among the three is most efficient?

Let total work to be done = 100 units

Let efficiency of A, B and C be $$a,b,c$$ units/hr respectively.

=> $$a+b+c=100$$ -----------(i)

A and B finish 60% of the work.

=> $$a+b=\frac{60}{100}\times100=60$$ -------------(ii)

Similarly, $$b+c=70$$ -----------(iii)

Substituting value from equation equation (ii) in (i),

=> $$c=100-60=40$$

Similarly, $$a=30$$ and $$b=30$$

Thus, C is the most efficient.

=> Ans - (C)