Grade 10 — Mathematics 10-3 › T3U03 Linear Measurement Problems

Grade 10 › T3U03 Linear Measurement Problems › L1
GRADE 10 · ALBERTAOUTCOME AB-MAT10-3-M3

L1 · Referents and estimating linear measurements

Learning goal

“I can pick a referent - a familiar object whose length I know - for any common SI or imperial unit, and use it to estimate lengths and the dimensions of objects before I measure them.”

Referent — a familiar object you use as a personal measuring stick: "about one door tall," "about six shoe-lengths." A good referent is always with you.
Estimate — a reasoned approximation, found by counting referents. It is not a guess: you can always say which referent you used and how many.
Linear measurement — a measurement of length in a straight line: a width, a height, a distance, a diameter.
Worked example

Estimate the height of a classroom whiteboard in metres, without a tape. Step 1: Choose a referent for 1 m: the height of a doorknob from the floor is about 1 m. That referent is always available. Step 2: Stack it mentally up the board: the board's height is about one doorknob-height. That is not the question - the board's LENGTH runs sideways: it spans about 3 doorknob-heights laid end to end. Step 3: Estimate ≈ 3 m. Say the whole sentence: "About 3 metres, because it is about 3 doorknob-heights long." An estimate without its referent is just a number.

Check yourself — explain it

Which is the best referent for 1 cm?

Paired problem — example still visible

Estimate the width of a textbook in centimetres using your fingernail referent. -> about 20-22 fingernail-widths, so ≈ 21 cm (accept 18-24 cm with the referent named).

Faded completion — last step is yours

"A water bottle is about 2 hand-widths tall. One hand-width is about 10 cm. The bottle is about 2 x 10 cm = ___ cm tall." -> 20 cm

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

Start practice →Take the unit quiz