What a map scale is

A scale is so essential that lines and shapes without one are only a sketch. A map scale gives the relationship between the map and the earth's surface it shows: the ratio of the distance between two points on the map to the distance between the same two points on the ground.

Fraction words used with scales:

• Numerator: the number above the line; in 1 : 50,000 it is 1 (the map distance).
• Denominator: the number below the line; in 1 : 50,000 it is 50,000 (the ground distance).
• Representative fraction (R.F.): a scale written as a fraction of a unit distance on the map to the distance in the same units on the ground.

Two systems of measurement:

• Metric system (used in India and many other countries): 1 km = 1,000 metres; 1 metre = 100 centimetres; 1 centimetre = 10 millimetres. So 1 km = 1,00,000 cm.
• English system (still common in the United States and the United Kingdom): 1 mile = 8 furlongs; 1 furlong = 220 yards; 1 yard = 3 feet; 1 foot = 12 inches. So 1 mile = 63,360 inches.
• India used the English system for distances before 1957.

From the video: the teacher's point is that a map distance is a straight, point-to-point distance. If Delhi and Mumbai are a few centimetres apart on a wall map of India, the scale tells you how many kilometres that is in a straight line; the road or railway distance will be longer.

Example (new): how many centimetres are in 3 km? 3 × 1,000 m = 3,000 m, and 3,000 × 100 = 3,00,000 cm.