Lesson Plan (Grades 6-8): Code-Your-Own Calculator

Lesson Title: Code-Your-Own Calculator

Grade Levels: 6–8

Subject Area: Mathematics & Computer Science

1. Introduction

Invite your students to step beyond the user interface and into the programmer’s seat by building their own digital calculators with block-based coding platforms such as Scratch. In this hands-on, collaborative lesson, learners will translate basic arithmetic and advanced functions into interactive code blocks. They will design button sprites for digits and operations, craft user interfaces that balance usability and style, and implement error-handling logic for cases such as division by zero or invalid inputs.

As teams program addition, subtraction, multiplication, and division buttons—and extend their calculators to include square, square-root, and exponent functions—they’ll test real examples, refine glitches, and compare multiple approaches. The activity culminates in a classroom showcase where every group demos their calculator, compares UI layouts, and reflects on the underlying math logic that makes digital calculators reliable. This lesson builds computational thinking, deepens students’ understanding of arithmetic processes, and strengthens problem-solving and collaboration skills.

2. Learning Targets

By the end of this lesson, every student will be able to:

• Translate Arithmetic into Code
  • Implement block-based event handlers that perform addition, subtraction, multiplication, and division.
• Program Advanced Functions
  • Add buttons for square, square-root, and exponentiation, wiring each to correct mathematical algorithms.
• Design Intuitive Interfaces
  • Sketch and build a clear on-screen layout, grouping numeric keys, functional keys, and display panels for ease of use.
• Handle Errors Gracefully
  • Detect invalid operations (e.g., dividing by zero, empty input, unexpected symbols) and display meaningful error messages.
• Collaborate & Debug
  • Work effectively in pairs to trace logic flows, identify and fix bugs, and peer-review each other’s code.
• Reflect on Math Logic
  • Articulate how their code enforces the order of operations and why certain safeguards (error checks) are mathematically necessary.

Each student will contribute to at least five coded functions, write two error-handling routines, and participate in the evaluation of three peer calculators.

3. Standards Alignment

This lesson supports key mathematics, technology, and engineering standards:

• CCSS.MATH.CONTENT.6.EE.B.5 Write, read, and evaluate expressions in which letters or symbols represent numbers.
• CCSS.MATH.CONTENT.7.EE.B.3 Solve real-world and mathematical problems posed with rational numbers, applying operations in correct sequence.
• CCSS.MATH.PRACTICE.MP6 (Attend to Precision) Emphasize exact variable naming, precise block placement, and consistent error messaging.
• NGSS.MS-ETS1-4 (Engineering Design) Develop a model to generate data for iterative testing and refinement of a prototype (the calculator).
• ISTE Standard 1 (Empowered Learner) Use technology to set and achieve learning goals, demonstrating proactive problem-solving.
• ISTE Standard 4 (Innovative Designer) Use a variety of technologies within a design process to identify and solve problems by creating new, useful artifacts.