Question

The scale on a map is `1:25000` .(A) find the distance in kilometres between two islands represented by a distance of `20cm` on the map. (B) find the distance between two towns on the map that are `10` kilometres apart?

Answer 1

`(A) 5 km`

`(B) 40cm`

Explanation:

Direct proportion is an easy way of working with scales.

The ratio `1 : 25000` has no specific unit, but once a unit is chosen, the unit is the same for both.

Let's use `cm` because that is the unit used.

`1cm : 25,000cm` means

`1cm` on the map represents :

`25,000 div 100,000 = 0.25 km`

Now you can compare `cm and km`

(A) `1/0.25 = 20/x" "(larr cm)/(larr km)`

`x = 0.25 xx20 = 5 km`

(B) `1/0.25 = x/10" "(larr cm)/(larr km)`

`x = 10/0.25 = 40cm`