Scale Factor, Volume, and Surface Area

Area and Volume Scale Factor

Y10 Miss Hancock

Yesterday you looked at Similar Shapes and finding missing lengths, this is known as the Length scale factor.

Today we are going to be looking at the AREA SCALE FACTOR.

Think about this question, the lengths have been multipled by 2, but what happens to the area?

Here is another example, look at the length scale factor compared to the area scale factor.

Have you spotted the rule!?

Multiple Choice

Did you spot the rule?

• No I don't understand

• Yes, the AREA scale factor is the LENGTH scale factor squared.

Multiple Choice

What is the area of triangle b?

• The length scale factor is 2, so the area scale factor is:

  $$2^2$$ = 4
  $$20cm^2$$ x 4 = $$80cm^2$$

• Length scale factor is 2, so 2 x 2 = 40 $$cm^2$$

Did you get it correct :) you may want to make some notes in your book.

If you are still feeling unsure then watch the video on the next slide.

NOW LET'S LOOK AT VOLUME SCALE FACTOR

Question, if the scale factor between the lengths is 2, the scale factor between the AREA is 2²

^{What would we multiply by to find the VOLUME scale factor?}

You guessed it! We multiply by 2³ for the volume! Let's look at an example question.

Multiple Choice

Work out the volume of prism b

• 405cm³

• 45cm³

• 9cm3

Here is an explanation of the answer, if you are still unsure watch the video on the next slide

Time to practice

Head to dr frost to start the questions 'Area and Volume scale factor'

Remember to click on the video at the top of the question if you need some help still!

You can present your screen and I can go through questions with you on dr frost as well, I will be on the meet.