When a full circle, i.e. 360°, is completed along the Earth's equator, the length of the equator is about 40,000 km. Degrees are divided in the same way as hours into minutes and seconds as follows: 1 o = 60 'and 1' = 60 ''.

a) How long is one nautical mile, or 1 part of the equator?



b) Vessel speeds are usually expressed in knots. One knot means one nautical mile per hour. In ports, the speed limit for vessels is 6 knots. What is this speed in kilometres per hour?