Making Big Plans

Lesson Plan - Get It!

Audio:

All kidding aside, we will be talking about scale drawings, and blueprints are the perfect scale drawing!

First, let's talk about scale.

Scale is the ratio between corresponding measurements of a blueprint and the actual object.

In the example below, the blueprint is 1 inch by 3 inches, while the actual object is 4 inches by 12 inches:

In this example, the scale would be 1:4. This means that for every 1 unit on the blueprint, there are 4 units on the actual object.

This could possibly mean that 1 unit (maybe an inch) on the blueprint could represent 4 inches (or even 4 feet!) on the actual object.

Let's do a basic scale problem:

Jim made a blueprint of the White House. Jim's blueprint used a scale in which 1 inch represents 6 feet. The White House has an actual length of 168 feet.

• What is the length in inches of Jim's blueprint?

We can solve this by setting up a proportion!

We will put the inches on the top of each fraction and feet on the bottom. We then cross-multiply and divide:

Therefore, 28 inches is the length in inches of Jim's blueprint

• Not too bad, huh?

Here's another one:

Lisa Ann drew the following blueprint of her store:

• If 1 inch = 4 feet, what is the area of the store?

This one is a little different and involves one more step, but we've got this!

• First, what would the dimensions of the store be?

We can set up proportions like before. However, this time we need to determine two different answers: the length and width in feet of the store.

We can see the dimensions of the store would be 20 feet by 36 feet:

• The question asked for the area of the store, so are we finished?

Nope! One more step!

• How do we find area of a rectangle?

The formula is A = lw, so we will multiply the length and width. This will give us 20 x 36, which is 720.

Therefore, the area of the store is 720 square feet!

Now that you have a handle on using and describing scale drawings, let's move on to the Got It? section.