Category Archives: rational numbers

Counting ropes and rational numbers

Contributed by Lori Hieresrich

πŸ“– Standard

Apply and extend previous understandings of addition and subtraction to add and subtract rational numbers; represent addition and subtraction on a horizontal or vertical number line diagram.

πŸ“ƒ Summary

The lesson begins with a discussion of record keeping methods in Indigenous cultures. Students will watch video on Incan counting ropes. Students will create their own number line counting rope. Students watch another video on number lines. Students will use their number line to find Absolute Value of an integer. Students will demonstrate understanding of adding and subtracting integers on number line.

⏰ Time

45- 60 minutes

πŸ“² Technology Required

The videos can be watched on any computer, phone or tablet. Not technology, but each student needs 2 yards of cord. ( As long as needed for all the knots with even spaces between.) Thicker cord is better to make it more tactile. Cord that works could be hemp, leather strips, or twine.


Start with this PowerPoint presentation. Also available as a Google Slides presentation.

NOTE: If you are using it as a PowerPoint presentation, download it before making any changes. Making changes to the PowerPoint in Google Drive will delete the animations and one of the embedded videos and you don’t want to do that.

The first five slides introduce the topic of how people from different Indigenous cultures in the Americas measured time and other quantities.

2. Watch this video on Quipu accounting

3. Make a counting rope

Students make their own counting ropes using rope, string or twine. Instructions to give students are provided in the PowerPoint.

4. Use the counting rope to solve math problems

Students follow along in the presentation to solve problems using positive integers , fractions and negative integers. The concept of absolute number is introduced, as well as the fact that adding the same number but with the opposite sign will always equal zero. If students are learning at home, they can complete the problems on their own.


In addition to the problems completed as a class in the presentation, students complete this worksheet with problems on using a number line with positive and negative integers and absolute value. Only print the first page. The second page is the answer key.

Number line and absolute value – word doc

Number line and absolute value – pdf

Differentiated instruction (optional)

Knots on a counting rope video or the children’s book by the same name give other examples of using a rope to count. This would be appropriate for younger children or those in the class who are at a lower grade level in reading proficiency.

Recommended Related Lesson

The Codex in Latin American history and math

Raising Sheep and Rational Numbers

πŸ“– Standards

Dine’ Culture Standards (3.PO2) I will develop an understanding of Dine’ way of life through Iina’. I will implement and recognize the Dine’ lifestyle. I will present the stories related to Land and Water Beings.

CCSS.MATH.CONTENT.7.EE.B.3 Solve multi-step real-life and mathematical problems posed with positive and negative rational numbers in any form (whole numbers, fractions, and decimals)

⏰ Time

45 minutes

πŸ“² Technology Required

Device with web-browser – Chromebook, laptop or desktop computer, phone or tablet

πŸ“ƒ Summary

Why would a Navajo sheep farmer need rational numbers? Our sheep farmer wants to build a new sheep corral. He would need to know positive and negative numbers, fractions, and decimals. This middle school lesson on rational numbers is integrated with some Navajo sheep history and is for grades 7 to 8. The examples are detailed and include word problems of rational numbers as applied to finding sheep farming profits. Operation rules are covered along with application of ratio and perimeter skills.

πŸ“š Lesson

1. Bell ringer: Navajo Sheepherding Life

Have students watch this short spotlight video of Navajo sheepherding life in Arizona.

2. Write answers to prompts

Write a short response to it to keep in their notes for discussion during the history parts of the lesson.

  • What do you notice about the northern Arizona terrain?
  • What do traditional Navajos think of land ownership?
  • How does the grandmother, Helen, care for her animals?

3. Math Lesson on Rational Numbers

This presentation, Raising sheep and rational numbers, introduces the concept of rational numbers as anything that can be explained as a ratio. Negative numbers are illustrated both as loans a sheep farmer would take out and depth of holes in the ground that the farmer needs to consider in selecting the size of posts. Students are given rules of integer addition and subtraction to use as an aid in solving problems.

4. Play Game

Play Making Camp Navajo – Sheep Herding and Rational numbers.

Select the game with this icon

Differentiated Instruction

For students who may need a review of the basics, this video on What are Rational provides a good and entertaining refresher.

Related Lessons

Adding and subtracting decimals — Students watch two videos explaining decimal and fraction equivalence. They are then presented with a brief reminder of natural, integer and rational numbers. A slide presentation discusses adding and subtracting decimals. The lesson ends with teacher and student-generated practice problems.


There are five problems within the presentation to be worked as a class. Teachers can present the question and have students write the answers and then present the answers. Alternatively, for students working at home, each slide with questions is followed by worked answers.

Teachers can also see which standards students have attempted and how many problems they have answered correctly in the Making Camp teacher reports.