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?

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Answer 1 · 2018-08-09T19:06:02

#(A) 5 km#

#(B) 40cm#

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#