Perimeters of polygons · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Perimeters of polygons

Mathematics · Measurement · ages 8-9
Name ______________________   Date ____________

  1. To find the perimeter of any polygon, what do you add together?

    • The area of each side
    • The length of every side
    • Just the two longest sides

  2. Nina says the perimeter of a shape is found by adding all of its sides. Is Nina right?

    Circle one:   True   False

  3. A square has sides of 7 cm. What is its perimeter?

    • 28 cm
    • 14 cm
    • 49 cm
    • 21 cm

  4. A rectangle has sides 6 cm and 3 cm. What is its perimeter?

    • 9 cm
    • 18 cm
    • 24 cm

  5. Two rectangles both have perimeter 24 cm: one is 10 by 2, the other 7 by 5. Which has the bigger area?

    • The 7 by 5 one
    • The 10 by 2 one
    • They are equal
    • You cannot tell

  6. A triangle has perimeter 30 cm. Two sides are 8 cm and 12 cm. How long is the third side?

    • 10 cm
    • 12 cm
    • 22 cm
    • 30 cm

  7. A pentagon has perimeter 30 cm. Four sides are 5 cm, 6 cm, 7 cm and 8 cm. How long is the missing side in cm?

    Answer: ______________

  8. Two rectangles both have a perimeter of 24 cm. Can they cover different amounts of space?

    • Yes, the sides can be split up in different ways
    • No, matching perimeters always mean matching areas
    • Only if one of them is a square

  9. A hexagon has six sides and a perimeter of 42 cm. Five sides measure 6 cm, 7 cm, 8 cm, 6 cm, and 7 cm. What is the length of the sixth side, in centimeters?

    Answer: ______________

  10. Ben says a rectangle with sides 10 cm and 2 cm has a perimeter of 12 cm. What mistake did he make?

    • He mixed up perimeter with area
    • He added the numbers incorrectly
    • He forgot a rectangle has two pairs of sides, not one of each
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Perimeters of polygons W1-mt_WtcFrxGOgw-s1

  1. The length of every side · Perimeter is the total distance around a shape, so you add up every side length.
  2. True · Perimeter is the total distance round a shape, found by adding every side.
  3. 28 cm · 4 equal sides of 7 cm give 4 x 7 = 28 cm.
  4. 18 cm · Add all four sides: 6+3+6+3=18 cm. A rectangle has two pairs of equal sides.
  5. The 7 by 5 one · 10 x 2 = 20 but 7 x 5 = 35, so the 7 by 5 rectangle covers more.
  6. 10 cm · 8 + 12 = 20, and 30 - 20 = 10 cm.
  7. 4 · Known sides add to 26, and 30 - 26 = 4 cm.
  8. Yes, the sides can be split up in different ways · 24 cm could be split as 4+8+4+8 or 6+6+6+6. Those rectangles look different and cover different areas.
  9. 8 · 6+7+8+6+7 = 34 cm. Subtract from 42: 42-34 = 8 cm.
  10. He forgot a rectangle has two pairs of sides, not one of each · Ben only added 10+2 once. A rectangle repeats each side length, so it should be 10+2+10+2=24 cm.
Worksheet · LightMySky