🔢 MathLevel 1Lesson 21
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Measuring with Nonstandard and Standard Units

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Learning Objectives

  • 1Measure the length of an object using nonstandard units (like paper clips or cubes)
  • 2Measure the length of an object using standard units (inches on a ruler)
  • 3Explain why standard units give the same answer every time
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Mini Lesson

Comparing told us which is longer or shorter. Now we go one step further — how much longer? That is what measuring is for!

Nonstandard units — any object the same size

  • A nonstandard unit is any object you use to measure — paper clips, cubes, erasers, or your finger.
  • Line the units end-to-end along the object, starting at one edge. Count how many fit.
  • Example: "My pencil is 6 paper clips long."
  • Problem: if two people use different-sized paper clips, they get different answers!

Standard units — everyone agrees

  • A standard unit is a unit everyone agrees on so measurements match everywhere.
  • In the US we use inches and feet (12 inches = 1 foot).
  • We use a ruler to measure in inches. The numbers on the ruler count the inches.
  • Always start measuring from the zero end of the ruler, not from the edge of the ruler itself.

How to read a ruler

  • Place the ruler so the 0 mark lines up with one end of the object.
  • Look at the number the other end reaches — that is the length in inches.
  • If the end falls between two numbers, read the closest whole number for Grade 1.
Pencil measured with 5 paper clips laid end to endA yellow pencil above five linked paper clips. Each paper clip is numbered 1 to 5, showing the pencil is 5 paper clips long.Nonstandard Unitspencil123455 paper clips longAny same-size object can be a unit!⚠ Different paper clip sizes= different answers!
A pencil measured with 5 paper clips laid end-to-end — a nonstandard unit example.
Ruler measuring a crayon at 4 inchesA ruler showing 0 to 6 inches. A blue crayon sits above it, starting at 0 and ending at the 4-inch mark. An arrow points to 4 with the label "4 inches".Standard Units (Inches)crayon01234564 inches!startat 0Everyone gets the same answer!
A ruler from 0 to 6 inches with a crayon ending at the 4-inch mark — a standard unit measurement.
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Ask yourself: "Did I start at zero? How many units long is the object?"

Vocabulary
Nonstandard unit
Any same-size object used for measuringe.g. paper clips, cubes, erasers, fingers
Standard unit
A unit everyone agrees on so measurements matche.g. inch, foot, centimeter
Ruler
The tool used to measure length in inchese.g. 12 inches = 1 foot
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