Work done by A in one day is half of the work done by B in one day. Work done by B is half of the work done by C in one day. If C alone can complete the work in 35 days, then in how many days can A, B and C together complete the work?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 20
Work done in one day is the fraction of the whole work finished in a day; working together, the fractions add up.
C alone takes 35 days, so C does \(\frac{1}{35}\) of the work a day
B does half of C’s work: \(\frac{1}{70}\) a day
A does half of B’s work: \(\frac{1}{140}\) a day
Together: \(\displaystyle \frac{1}{140}+\frac{2}{140}+\frac{4}{140}=\frac{7}{140}=\frac{1}{20}\) a day
They finish the work in 20 days