Math · Stage 6

Similar shapes, enlargement and scale factor

Similar shapes are the same shape but can be different sizes: matching angles stay equal and matching sides keep the same ratio. Multiply every side by the scale factor to enlarge, and divide a matching pair of sides to find the scale factor.

✦ Math📘 Stage 6 · S6⏱ ~14 min🧒 Ages 10–12★ Free to start

I can enlarge shapes and use the scale factor.

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Kavi Blows Up a Photo 🔍

Kavi drags the corner of a tiny photo and it grows — the owl stays the same owl, just bigger! “A copy that is the same shape but a different size is a similar shape,” hoots Kavi. “The scale factor is the number I multiply every side by. Scale factor 3 makes each side 3 times as long. To go back the other way I divide a new side by its matching old side. The angles never change — only the sizes do.”

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What your child will learn

1What a scale factor doesSimilar shapes are the same shape but can be different sizes. The scale factor tells you how much bigger or smaller: new length = old length × scale factor. Tap each idea to see how it works.

2Does the scale factor enlarge, shrink or keep the same?

3Multiply to enlarge · divide to find the scale factorUsing a scale factor is always one of two moves. Tap each card to see which.

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A peek inside

A triangle has a side of 6 cm. Kavi enlarges it by scale factor 4. How long is the matching side now?

new length = old length × scale factor = 6 × 4 = 24

Try this at home: A 5 cm side is enlarged by scale factor 3. How long is it now?

Ready to play and learn?

Start the free interactive lesson, or print the handout for screen-free play.

Start the free lesson →⬇ Download PDF

Part of Math · Stage 6 · S6 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.