Practical: Working with map scales
Scale is shown in three ways. A numerical scale is written as a ratio: 1:50 000 000 – 1 cm on the map equals 50 000 000 cm on the ground. Since 1 km = 100 000 cm, 50 000 000 cm = 500 km. A named scale states this in words: “1 cm to 500 km”. A linear scale is a line whose divisions are marked in kilometres. To find a real distance from the map, multiply the map distance (cm) by the distance that 1 cm stands for. In the reverse problem divide the real distance by the distance in 1 cm to get the map distance. To change a numerical scale into a named one, remove five zeros to convert cm to km: 1:1 500 000 – 1 cm to 15 km (1 500 000 cm = 15 km). Measure distance with a ruler along a straight line; if the route is curved, measure with a string.
Practical work: 1) draw your classroom dimensions (say 10 m and 6 m) at 1:100 in your notebook (10 cm and 6 cm); 2) draw a sketch of your route from home to school at a scale you choose; 3) measure the distance between two cities on a map with a ruler and calculate it in kilometres. Safety: measure inside the class with a tape; go out on a street to measure a route only with adults.