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!