Use Ratio to Solve Scale Drawing Problems

In this activity, we will use ratio to find missing missing lengths in scale drawings.

 

A scale drawing is used when designs are made.

From toy cars being a scale model of actual cars, to high rise buildings having models made before being built.

 

The scale in a scale drawing is often shown as a ratio.

A ratio of 1:100 means that 1 cm on the drawing represents 100 cm in actual real life.

This could also be written as 1 cm:1 m or 1 cm to 1 m.

 

This means that a scale of 1 cm to 5 m could also be written as 1:500 because there are 100 cm in one metre.

 

Let's look at a question!

 

Example

An  American car company want to make a scale drawing to celebrate their new car!

The model will be 1 : 200

If the actual car height is 1.6 metres, what would the scale model height be?

 

Answer

The ratio is 1 cm to 200 cm

The actual height is 1.6 m

We need to convert 1.6 m into cm: 1.6 x 100 = 1,600 cm

 

How did we get from 200 cm to 1,600 cm? We can work that out by doing 1,600 ÷ 200 = 8

So, we multiplied 200 cm by 8 to get 1,600 cm.

We need to do the same thing to the other side of the ratio: 1 x 8 = 8 cm

The model height will be 8 cm

 

 

Let's try some questions like this!