MAT1793-ABED_1: Linear Referents

Constructing Knowledge

In the Getting Into It activity, various lengths were 'referred' to in terms of toilet paper squares. The square of tissue is called a referent. It is something that you can 'refer to' when thinking or talking about the length of an object.

The hand is another example of a referent. It is used in reference to the height of a horse. A hand has become a standard unit of measure over the years, but it began as a referent.

A referent is an object of known size that can be used to estimate unknown measurements. Referents are only used when an estimated measurement is needed. A referent is not an actual measurement or unit.

Be careful when choosing a referent. Some items may not be uniform in size/length. A pencil can change length depending upon how many times it has been sharpened. However, most pens are around the same length. You will also want to choose familiar items as referents.

Uniform objects have a standard size that does not vary significantly from one object to the next.

You can use your own body parts as linear referents if you know the approximate length of the body parts. Since people are different sizes, using a body part as a referent is personal. For example, a man might know his foot is close to 1 ft in length. This would make estimating the length of a room, in feet, fairly straight-forward. However, a child's foot might be closer to 0.5 ft.

Body Parts for Referents
body part	picture	approximate measure
finger width		1-2 cm or 1 inch
handspan		15-30 cm or 7-12 inches
foot		15 cm - 45 cm or 0.75 feet - 1.5 feet
arm span		1.5 m - 2.5 m or 5 feet - 7 feet
stride length		0.75 m to 2 m or 1-2 yards