geometry · Year 6 · Suggested learning sequence
Enlargement
An enlargement makes a shape bigger without changing its shape. The scale factor tells you how many times bigger: with a scale factor of 3, every length is multiplied by 3. It is never 'add 3'. To find the scale factor, pick a pair of matching sides and divide: new length ÷ original length. To find a missing length on the image, first find the scale factor from a pair you know, then multiply the matching original side by it. The angles stay the same; only the lengths grow.
Sample questions
This rectangle is enlarged by a scale factor of 2. How long is the image of the side marked 6 cm?
- A scale factor of 2 multiplies every length by 2.
- 6 × 2 = 12.
- The image of that side is 12 cm.
Answer: 12
This rectangle is enlarged by a scale factor of 3. How long is the image of the side marked 5 cm?
- A scale factor of 3 multiplies every length by 3.
- 5 × 3 = 15.
- The image of that side is 15 cm.
Answer: 15
This rectangle is enlarged by a scale factor of 3. How long is the image of the side marked 4 cm?
- A scale factor of 3 multiplies every length by 3.
- 4 × 3 = 12.
- The image of that side is 12 cm.
Answer: 12