meters and centimeters

Question

On a blueprint a square with 20 m per side was shown as a square with 12 centimeters per side. How long would a girder appear on the blueprunt if the girder is actually 15 meters long 

Answer 1

So if 12 cm represents 20 m, we need to find how many (X ) cm which represents 15 m.

 

So,  12cm/20m = Xcm/15m

 

Cross multiply:

15 x 12 =20X

180 = 20X

X = 9

9 cm represents 15 meters