A can complete a certain work in 30 days. He started the work. After 4 days, B joined him and the whole work was completed in 10 days from the beginning. B alone can complete one-third of the same work in:
Answer & explanation
Correct answer: option 2
A = 30 days,
Lets' take A's efficiency as 1,
Therefore, total work = 1 x 30 = 30 units, ..(Efficiency × Days = Total work)
⇒ A worked for 4 days = 1 x 4 = 4 units,
⇒ Remaining work = 30 - 4 = 26 units,
⇒ B joined A and they complete 26 units in 6 days = \(\frac{26}{1+B}\) = 6 days,
⇒ B = \(\frac{10}{3}\) (Efficiency)
⇒ Time required by b to complete \(\frac{1}{3}\)rd of the work = \(\frac{1}{3}\) x 30 = \(\frac{10}{10/3}\) = 3 days, ..(\(\frac{Work}{Efficiency}\) = Time)