Arun and Tarun can do a work in 10 days.After 4 days tarun went to his village.How many days are required to complete the remaining work by Arun alone.Arun can do the work alone in 20 days. Choose the correct option.
A) 12 days . B) 17 days . C) 18 days . D) 19 days . E) 20 days .

Rationale: "they together completed 4 / 10 work in 4 days . balance 6 / 10 work will be completed by arun alone in 20 * 6 / 10 = 12 days . answer : a"
Answer: A