UP Police SI Exam 19 Dec 2017 Shift 2 Solved Paper

Among the four people Sachin, Sourav, Yuvraj, and Dhoni, Sachin takes three times as long as Sourav to do a work. To complete the same work, Sourav takes three times as long as Yuvraj, and Yuvraj takes three times as long as Dhoni. A group of three out of four people can do the work in 13 days, while another group of three people can do the same work in 31 days. Which is the group that takes 13 days to complete the work?