Measure with Different Length Units

Students measure the same object twice using two different units (e.g., inches and centimeters, or feet and inches) and record both measurements. Students discover that larger units produce smaller numbers and smaller units produce larger numbers.

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Grade 2 · Measuring Length · question 1 of 3

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12 rungs. A star at the top.

Measure the stick in cm.

Your answer:

How it is taught

0:00 of 3:03

The same stick can be read in two units.

The smaller unit gives a bigger number.

Read it: Small units, more of them

One pencil, two rulers, both starting at 0. It is 15 centimeters, and about 6 inches.

Line the pencil up with 0 on both rulers.
Read it in centimeters, then in inches.
Say which unit needs more of them: centimeters.

The pencil does not change. Only the unit we count with changes.

A centimeter is smaller than an inch, so more of them fit along the pencil.

An inch is bigger, so fewer of them cover the same pencil.

Measure one thing in two units: the smaller unit takes more of them.

Thinking the pencil is longer in centimeters, because 15 is more than 6.

It is the same pencil. 15 small centimeters cover what 6 bigger inches cover.

A rope measures 24 inches, or 2 feet. Which is the bigger unit? — foot. The same rope takes fewer feet (2) than inches (24), so a foot is the bigger unit.

Measure one pencil in inches AND centimeters

Today we'll measure the same pencil two different ways. Will we get the same number? Let's find out!

Here is our pencil. We want to know how long it is.

Here's a ruler that measures in inches.

Grade 2 · Same pencil, two different rulers

We line up the pencil at zero and count the inches all the way to the tip.

The pencil is six inches long. Six is our first number.

Now let's measure the same pencil with a centimeter ruler. Centimeters are smaller than inches.

We line up at zero again and count the centimeters.

This time we get fifteen centimeters!

Wait — the pencil didn't change. But our number did: six and fifteen.

Smaller units, like centimeters, need MORE of them. So the number is bigger.

Same pencil, two answers: six inches OR fifteen centimeters. The unit always changes the number!

Now you try. Read this object's length on the ruler. How many units long?

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics

Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal: 1 star — one skill mastered, every rung of its ladder climbed
Climbing now: Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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