Investigating area and perimeter

This investigation is a follow up to 'Playing with tessellations'.

Instructions

• Draw and cut out 2 equilateral triangles.

• Draw a squiggly line from one corner to another. Cut along the squiggly line.

• Stick the part you cut off on another side using sticky tape to create a new shape.

• Measure the perimeter of the triangle by guiding the rope around the three edges of the triangle.

  • Make a mark on the rope to show the length of the perimeter.

• Measure the perimeter of the new curvy ex-triangle by guiding the rope around the edges of the shape. Make a mark on the rope to show the length of its perimeter.

• Use a ruler or measuring tape to explore the difference.

  • Is the perimeter of your shapes the same or different?

  • If one shape’s perimeter is longer than the other, how much longer is it?

• Is the area of your shape the same or is it different?

  • Cut your shape back up in its pieces and use direct comparison to see if the area changed.

Discuss/reflect

• Can you change a shape so that the area and perimeter stay the same?

• Find some other shapes to explore. What would happen if we created a new shape out of a square, hexagon or a different type of triangle would the perimeter change or would it stay the same?

Share/submit

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