Farjan and Kashif can complete a task in 30 days. Farjan leaves after 20 days and Kashif alone completes it in another 25 days. How many days does Farjan alone take to complete the entire task?

A. 50
B. 75
C. 60
D. 45

Part of work completed by Farjan and Kashif in a day
= 1/30 Part of work completed by them in 20 days
= 20/30 = 2/3 1/3 of the work is remaining. Kashif completes 1/3rd of the work in 25 days. Part of work completed by him in a day
= (1/3)÷25
= 1/75 (1/D)+(1/V) = 1/30 (1/D) = (1/30)-(1/75) = 1/50 Farjan can complete it in 50 days.