Rulers, Yardsticks, and Meter Sticks - Second Grade Mathematics
Measurement is the bridge that connects the physical objects of our world to the precise realm of numbers, allowing us to build furniture, construct houses, make clothes that fit, and compare the heights of growing living things. To measure length—the distance from one end of an object to the other—mathematicians use specialized measuring tools designed for different sizes and shapes of objects. In this chapter, you will explore the three most important linear measurement tools—the 12-inch ruler, the 3-foot yardstick, and the 100-centimeter meter stick—and learn how to select the most appropriate tool for any measuring task you encounter.
The Three Standard Linear Tools
Let us compare the three primary tools used for measuring straight physical lengths.
The Linear Measurement Toolkit:
1. The 12-Inch Ruler:
|---|---|---|---|---|---|---|---|---|---|---|---|
0 1 2 3 4 5 6 7 8 9 10 11 12 (inches)
Length: 12 inches (exactly 1 foot). Best for: Small, handheld items.
2. The Yardstick:
+-------------------------------------------------------+
| 36 INCHES |
+-------------------------------------------------------+
Length: 36 inches (exactly 3 feet). Best for: Medium-to-large furniture, walls.
3. The Meter Stick:
+-------------------------------------------------------+
| 100 CENTIMETERS |
+-------------------------------------------------------+
Length: 100 centimeters (1 meter). Best for: Metric measurement of rooms, tracks.
The 12-Inch Ruler
A standard customary ruler is 12 inches long, which is equal to 1 foot. Rulers are rigid, portable, and fit comfortably inside a student desk or backpack. A ruler is the ideal tool when measuring small, flat objects that you can hold in your hands: a pencil, an eraser, an index card, a notebook, or a juice box.
The Yardstick (36 Inches / 3 Feet)
A yardstick is a long wooden or metal bar measuring exactly 36 inches, or 3 feet (since 3 x 12 = 36). It is three times as long as a standard ruler! A yardstick is the tool of choice when measuring medium-to-large straight objects that are too long for a single ruler: a student desk, a doorway width, a chalkboard, a guitar, or a bookshelf.
The Meter Stick (100 Centimeters / 1 Meter)
A meter stick is the primary tool of the international metric system, measuring exactly 100 centimeters, or 1 meter. A meter stick is slightly longer than a yardstick (1 meter is about 39 inches, compared to a yardstick's 36 inches). A meter stick is used when measuring objects in metric units: classroom tables, hallways, banners, and science experiments.
The Flexible Measuring Tape: Conquering Curves
What if the object you want to measure is not flat and straight?
The Measuring Tape:
____________________________
/ __________________________ \
| | | | | | | | | | | ====> Flexible ribbon curves around
| | 0 1 2 3 4 5 | | | round, irregular objects!
\_\__________________________/_/
Measuring Curved and Round Objects
Try measuring around your wrist, around a basketball, or around the trunk of a tree with a rigid wooden ruler: the stiff ruler cannot bend, so you cannot measure the curve! A measuring tape is made of flexible fiberglass, cloth, or thin metal that bends easily around three-dimensional objects. Whenever an object has curves or corners, a measuring tape is the correct tool.
Selecting the Appropriate Tool
Choosing the right tool is the first step in successful measurement. Using a tiny 12-inch ruler to measure a 50-foot playground basketball court would be tedious and full of counting errors, while using a giant yardstick to measure a tiny paperclip would be clumsy.
Tool Selection Decision Chart:
Object to Measure: Best Tool: Reason:
Crayon or Pencil 12-Inch Ruler Small, handheld, under 12 inches.
Large Reading Table Length Yardstick / Meter Stick Medium size, flat, several feet long.
Around a Pumpkin or Ball Measuring Tape Curved 3D surface requires flexibility.
Classroom Wall Width Measuring Tape (Long) Long distance, faster than repeating sticks.
Width of a Textbook 12-Inch Ruler Flat, fits comfortably within 12 inches.
Practice Exercises
Exercise 1: Name the three linear measuring tools discussed in this chapter, and state the exact length and units for each tool.
Exercise 2: Which tool would you choose to measure the length of a classroom whiteboard: a 12-inch ruler, a yardstick, or a flexible measuring tape? Explain your choice.
Exercise 3: Which tool would you select to measure the distance around your waist to see what size belt fits: a wooden yardstick or a cloth measuring tape? Explain why.
Exercise 4: Explain why measuring the length of a long hallway with a 12-inch ruler is more likely to cause mistakes than using a long measuring tape.
Solutions and Explanations
Solution to Exercise 1: The three tools are: the 12-inch ruler (length = 12 inches, or 1 foot), the yardstick (length = 36 inches, or 3 feet), and the meter stick (length = 100 centimeters, or 1 meter).
Solution to Exercise 2: A yardstick (or meter stick) is the best choice for a classroom whiteboard. A whiteboard is several feet long and has a flat, straight edge. Using a yardstick covers 3 feet in a single measurement, making it much faster and more accurate than laying down a short 12-inch ruler repeatedly.
Solution to Exercise 3: A cloth measuring tape is the correct tool because a waist is a curved, circular three-dimensional shape. A wooden yardstick is rigid and straight, meaning it cannot bend around the body to measure circumference.
Solution to Exercise 4: Measuring a long hallway with a 12-inch ruler requires laying the ruler down, marking the endpoint with a pencil, picking up the ruler, lining it up again, and repeating this process dozens of times. Every time you lift and reposition the ruler, small gaps, overlaps, or alignment shifts can occur, and it is easy to miscount the running total of feet. A long measuring tape rolls out continuously in one straight line, eliminating alignment errors.