Grade 2 › G2U08 Measuring Length

Grade 2 › G2U08 Measuring Length › L4
GRADE 2 · ALBERTAOUTCOME AB-G2-2M1

L4 · Referents for a centimetre; estimating length

Learning goal

“I can name a referent for 1 centimetre, and I can estimate a length by picturing my referent going along it again and again.”

Referent — a familiar thing you know the length of, used to think about other lengths. The width of your fingernail is a referent for 1 centimetre.
Estimate — a smart guess about a length, made before you measure. An estimate is an "about" number.
About — close to a number, but not exactly it. "About 9 cm" means near 9 cm.
Visualize — to picture something in your mind, like seeing your fingernail move along a ribbon.
Worked example

Kai needs a referent: a thing he always has with him that is about 1 cm. Step 1: He holds his fingernail beside a centimetre cube. The width of his fingernail matches the cube. Step 2: He says his referent: "My fingernail is about 1 cm wide." Step 3: Now he can think in centimetres anywhere: anything as wide as his fingernail is about 1 cm. Say it plainly: a referent is a known length you carry in your mind. For 1 centimetre, a fingernail width is a good referent.

Check yourself — explain it

Why is a fingernail a good referent for 1 centimetre?

Paired problem — example still visible

Which is also about 1 cm: the width of a paper clip, or the length of a shoe? -> the width of a paper clip

Faded completion — last step is yours

"A referent is a ___ thing whose length you know. My fingernail is a referent for ___ centimetre." -> familiar; 1

Ready to practise?

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

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