Question: Why do kids struggle to measure to the nearest fraction of an inch?
Answer: Rulers are so full of information that kids suffer information overload.
I love watching skilled teachers at work and my friend Nan is one of the best. Here is a 10-minute activity she thought up that kids loved. At the end of it, they had become ruler pros.
Objective: Have students describe a ruler so that someone who has never seen one before can draw it.
Easy set-up: Project the image of a ruler on your white board, or distribute rulers to pairs of students.
Ground rules: Students take turns giving clues. The teacher attempts to draw exactly what the students describe. Each student may give only one clue.
Managing group discussion: Have speakers hold an object like a pointer or a bean bag. Students then know whose turn it is to speak.
Here is a peek into how this activity played out in Nan’s classroom.
Nan: “I don’t know what a ruler is. Help me picture what it looks like!”
Student 1: “It is a stick with lots of little marks on it. And numbers 0 to 12.”
Nan draws a line with random tick marks and numbers all bunched together.
Student 2: “NO! Not like that. The marks are evenly spaced.”
Nan: “Tell me more. What do you mean evenly spaced? Are they all the same size? Are they all the same distance apart?”
Student 3: “OK! OK! Stop! Start over. First draw a long skinny rectangle. Then mark off numbers 0 to 12. But you have to make equal spaces.”
Nan starts a new drawing, using the new clues.
Student 4: “Yeah, like that. Now put a little mark above each number. It should be about half as wide as the rectangle. NO! I mean half as tall.”
Student 5: “Now you need to put more marks between the numbers.”
Nan: “Where should they go? Are they all the same size? How many of them do I need to draw?”
You get the idea. Nan asked clarifying questions to help her 23 students refine their clues. Students were engaged in solving the problem, used math language, visual analysis, and verbal descriptions, and gained important understandings of what the different-length ticks on a ruler show.
Here are some patterns students discovered:
1) The inch ticks on a ruler are longer than any other ticks.
2) The half-inch ticks are exactly midway between the inch ticks and are shorter than the inch ticks.
3) Other ticks are halfway between inch ticks and half-inch ticks. These are quarter-inch ticks and are shorter than the half-inch ticks.
4) There are tiny ticks halfway between the quarter-inch ticks. These are eighth-inch ticks and are the shortest.
Now students were ready for skillful ruler use to measure everyday objects to the nearest fraction of an inch.
Nan used this activity as part of her unit on fractions. Ruler skills reinforce and deepen a knowledge packet related to fractions and mixed numbers. Ruler skills help students locate fractions and mixed numbers on a number line, compare and order rational numbers, and understand the meaning of half of a half, and half of a fourth.
Try it yourself! If you’d like to share your own ideas, click here and then click Contact! Let’s all work together!