If 30 oxen can plough $$\frac{1}{7}$$ th of a field in 2 days, how many days 18 oxen will take to do the remaining work?

A. 30 days

B. 20 days

C. 15 days

D. 18 days

E. 21 days

Answer: Option B

Solution(By Examveda Team)

We will use work equivalence method,
$$\eqalign{ & \frac{{30}}{{18}} = \frac{{ {\frac{1}{7}} }}{{ {\frac{6}{7}} }} \times \frac{x}{2} \cr & \frac{5}{3} = {\frac{1}{6}} \times \frac{x}{2} \cr & Or,\,x = \frac{{60}}{3} = 20\,{\text{days}} \cr} $$