MATH: Doodle-Number Line (Adding and Subtracting Using a Number Line)

Time Required: Two 45-minute sessions
Skill Level: Beginner
Recommended Grades: K to 2nd

In this activity, students will work in pairs to practice adding and subtracting single and double-digit numbers in order to reveal a stencil of a robot inside a hundreds chart. Students will cross off the answer to each equation on the related worksheet and create their own Robo-Doodle.

*This lesson is geared for high-level math students who need an additional challenge in grades 1 and 2.

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Lesson Plan



Take students on a nature walk to collect pine cones or have students bring in pine cones from home. Be sure inform students to find opened pine cones.

Step 2

Call students to the whole group: Project your tablet or screen on the board for students to view the Pine Cone Data Sheet. Note the scales on the pinecone. Count them with the students. Enter the total on the Pine Cone Data Sheet. *Note that the word “data” means information.

Step 3

Share the goal: Today we will doodle pine cone scales with different colors, then work with the numerical significance of the scales in order to learn about fractions. We will compare the number of scales in each specific color to the total number of scales in the form of a fraction.

Step 4

Ensure students have their pine cones ready. Have each student in a pair count the total number of scales on their individual pine cones, and then get the students to compare their totals. Recount if they are different. Hand out one Pine Cone Data Sheet to each student and pencils for each pair to record their total of pine cone scales.

Step 5

Model how to use 6 colors to doodle each tip on your pine cone. You may work in a pattern, or doodle intermittent scales. Doodle the scale's tip in one spot, holding your 3Doodler steady for about 3 seconds. Then press the warm plastic down onto the scale with your finger to form a smooth cover.

*See reference images.

Step 6

Instruct students how to fill in the names of the colors used on the Pine Cone Data Sheet and fill in the total number of scales doodled in each color. Then instruct students how to record the number of each color as the numerator (top number) and the total of scales as the denominator (bottom number) for their fractions.

Step 7

Hand out the 3Doodlers and the Pine Cone Data Sheets for students. Circle to assist and assess as students work.

Step 8

Have the students in the pairs compare the data in their pinecones and worksheets.

Wrap Up

Students will share their Robo-Doodles with the whole class. Teacher will post the students' Robo-Doodles on Twitter. @3Doodler #3DoodlerEDU


The teacher will assess students’ understanding of the number line strategy by circling and assessing as students work, as well as each pairs solutions on the worksheet and hundreds chart.

Possible Extensions

Students will select an addition or subtraction problem from the worksheet and write a word problem about it in which their Robo-Doodle is a character in the problem. Example: Robo-Doodler orders 30 pizzas. His robot friends eat 4 of them. How many are left?


  • addition - the act or process of adding.

  • collaboration - to work jointly with others or together especially in an intellectual endeavor.

  • counting numbers - Any number you can use for counting things: 1, 2, 3, 4, 5, ... (and so on).

  • number line - a straight line on which there is indicated a one-to-one correspondence between points on the line and the set of real numbers.

  • problem-solving - the process or act of finding a solution to a problem.

  • subtraction - the operation of deducting one number from another.

  • whole number - A whole number is a number without a fractional or decimal part, and with no negative values (i.e., 1, 2, 3...500, 501, etc.).

Educational Standards

Common Core

Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

In This Lesson

Students will solve addition problems by doodling forward (addition) or backward (subtraction) on a number line and crossing off answers on a hundred chart.

CS Teachers

Decompose (break down) a larger problem into smaller sub-problems with teacher guidance or independently.

In This Lesson

Students will break down the process of adding and subtracting with double-digits by doodling on a number line and crossing off answers on a hundred chart.


Use technology to seek feedback that informs and improves their practice and to demonstrate their learning in a variety of ways.

In This Lesson

Students will use the 3Doodler to doodle on a number line and doodle the outline of a stencil revealed on a hundred chart.

Common Core

Create original works or responsibly repurpose or remix digital resources into new creations.

In This Lesson

Students will use a 3Doodler to doodle a Robo-Doodle, then fill and embellish it.


Use collaborative technologies to work with others, including peers, experts or community members, to examine issues and problems from multiple viewpoints.

In This Lesson

Students will seek feedback from peers as they solve addition problems, assign colors and doodle with the 3Doodler.

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