A boat can go 9 km downstream and 4 km upstream in 21⁄2 hours. It can go 15 km downstream and 6 km upstream in 4 hours. How much time will it take to go 8 km downstream and 10 km upstream?

Ramesh covers 56 part of the total distance by bus and the remaining 36 km by car. What is the total distance of his journey?

A person covers a distance of L km in 12 hours. If he increases his speed by 10 m/s, he covers the same distance in 8 hours. Which of the following statements is/are correct? I. The value of L is 760 km. II. The original speed of the person is 72 km/h.