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

Guessing Length Before You Measure

Mathematics · Measurement · ages 7-8
Name ______________________   Date ____________

  1. Kai estimates his desk is 60 cm long. Measuring shows 58 cm. How many centimetres out was his estimate?

    Answer: ______________

  2. A book is 15 finger-widths wide. Each finger-width is about 1 cm. Which estimate is most reasonable?

    • 15 cm
    • 5 cm
    • 150 cm
    • 1 cm

  3. What do we call a smart guess about how long something is, made before you measure it?

    • An estimate
    • An answer
    • A ruler

  4. After you estimate a length, you should measure it to see how close your guess was.

    Circle one:   True   False

  5. A pupil estimates a shelf is 90 cm long. It actually measures 87 cm. How many centimetres out was the estimate?

    Answer: ______________

  6. You want to estimate how tall a bookshelf is. Which reference is most helpful?

    • Your own height, since you know about how tall you are
    • The weight of a book
    • The colour of the shelf

  7. Which is the most reasonable estimate for the height of a classroom door?

    • 2 cm
    • 2 mm
    • 20 m
    • 2 m

  8. Max says his little fingernail is about 1 m wide. Is Max right?

    Circle one:   True   False

  9. Leo estimates the length of his classroom whiteboard is 500 metres. What is wrong with his estimate?

    • The estimate is exactly right
    • 500 metres is way too long for a whiteboard; he probably meant a much smaller number
    • Whiteboards are always measured in metres

  10. Lena estimates the board is 120 cm wide, then measures 124 cm. How many centimetres out was she?

    Answer: ______________

LightMySky · lightmysky.comW1-mt_OzRZ89GrQW-s1

Answer key

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

Guessing Length Before You Measure W1-mt_OzRZ89GrQW-s1

  1. 2 · 60 - 58 = 2 cm out.
  2. 15 cm · 15 lots of about 1 cm make about 15 cm.
  3. An estimate · An estimate is your best guess about length before you check with a ruler or tape.
  4. True · Checking your estimate against the real measurement tells you how good your guess was.
  5. 3 · 90 - 87 = 3 cm out.
  6. Your own height, since you know about how tall you are · Comparing the shelf to your own height gives you a useful starting point for a guess.
  7. 2 m · Doors are a little taller than people, about 2 m.
  8. False · Max is wrong. A fingernail is about 1 cm wide, and 1 m is a hundred times bigger.
  9. 500 metres is way too long for a whiteboard; he probably meant a much smaller number · 500 metres is about five football fields long. A whiteboard is only a metre or two wide.
  10. 4 · 124 - 120 = 4 cm out.
Worksheet · LightMySky