Two boars, travelling at 5 and 10 kms per hour, head directly towards each other. They begin at a distance of 20 kms from each other. How far apart are they (in kms) one minute before they collide?

In the final one minute before collision, the two boats travel 5 X 1/60 km and 10 X 1/60 km i.e

1/12 km and 1/6 km. As they move in opposite directions, distance between the boats one minute before collision is 1/12 + 1/6 = 1/4