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.

Note: Any links outside of are optional resources. We can’t ensure their upkeep or accuracy.


Students have
  • practiced with the 3Doodler.

  • had practice drawing straight lines, outlines and fill with the 3Doodler.

  • practiced addition and subtraction with single and double-digits.


Students will
  • correctly solve addition and subtraction problems using single and double-digit numbers.

  • use a hundred chart to decipher the stencil of a Robo-Doodle.

  • use a 3Doodler to outline, fill and embellish their Robo-Doodle.


Students will need

Lesson Plan



Print a Robo-Doodle Worksheet for each pair of students.

Step 2

Project your tablet or computer screen on the board for students to view the Robo-Doodle Worksheet, and show the Hundred Chart on page 2 of the document.

Step 3

Demonstrate how to use a number line as means to use addition and subtraction. Project the Doodled Number Line and use a 3Doodler to move forward for addition and backward for subtraction.

Step 4

Model how to cross off worksheet answers on the hundred chart. Explain to the students that as they cross off answers, they will, little by little, reveal an image/stencil to doodle.

Step 5

Share this riddle as a hint: I have never gone to school, but I am smart. Who or what am I?

Step 6

After students have solved and crossed off all answers, check their work to see if they've revealed the Robo-Doodle.

Step 7

Model how to outline, fill and personally embellish a Robo-Doodle. Note that larger fill areas may be sectioned off into smaller areas for easier filling.

Step 8

Hand out 3Doodlers, Robo-Doodle Worksheeta and
Doodled Number Line Woeksheets. Circle to assist and assess as students work.

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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