Homework Help

Step by Step help for homework sheet on ratios in

maps.

1.  The scale of a map is 3 cm = 2 km map:  1 cm

actual:  ________ kmThis is really a simple ratio problem. The scale of the map can be stated as 3:2

This means that if you measure 3 centimetres on the map, it represents 2 kilometres in real life.

Set up equivalent fractions, make sure you note which term is represents

x

1

2

3

cm

km

The missing information is km, so the ϰ must go as the denominator (bottom) because in the original ratio, we put kms on the bottom.

Cross multiply as usual

ϰ = 0.66666 kms. Round off to hundredths. (two decimal places)

ϰ = 0.67 kms.

If you can’t remember how

to cross multiply or round off, go

to the math website and

review.

2.  The scale of a map is 3 in = ____ mi

map:  1 in actual:  4 mi

This is still the same type of question. In this example, you need to calculate the scale.

You still set up equivalent fractions, taking care to make sure that each term is where it belongs

4

13x

Inches

Miles

Remember to note what

each term represents.

Cross Multiply as Usual

ϰ = 12 miles

Make sure you include the right unit (in this case miles) for your answer.