Decomposition (breaking problems down) in Intro to Computing - Draw & Build Visually

Draw This - beginner

Draw a flowchart to show how to make a cup of tea by breaking the task into smaller steps.

10 minutes

Hint 1

Hint 2

Hint 3

Grading Criteria

Start and End oval symbols present

Main task broken down into at least 5 smaller steps

Steps represented by rectangles

Flow direction clearly shown with arrows

Logical order of steps for making tea

Solution

  _________
 /         \
|  Start   |
 \_________/
      |
      v
  _______________
 | Boil water    |
 | (fill kettle) |
 | and switch on |
  ---------------
      |
      v
  _______________
 | Place tea bag |
 | in cup       |
  ---------------
      |
      v
  _______________
 | Pour boiling  |
 | water into cup|
  ---------------
      |
      v
  _______________
 | Let tea brew |
 | for 3-5 mins |
  ---------------
      |
      v
  _______________
 | Remove tea   |
 | bag          |
  ---------------
      |
      v
  _______________
 | Add milk or  |
 | sugar if you |
 | want        |
  ---------------
      |
      v
  _________
 /         \
|   End    |
 \_________/

This flowchart starts with the task of making tea. It breaks the task into smaller steps:

• Boil water by filling the kettle and switching it on.
• Place a tea bag in the cup.
• Pour the boiling water into the cup.
• Let the tea brew for 3-5 minutes.
• Remove the tea bag.
• Add milk or sugar if desired.

Each step is shown as a rectangle, and the process flows from start to end using arrows. This shows how decomposition breaks a big task into smaller, manageable steps.

Variations - 2 Challenges

[intermediate] Draw a flowchart to show how to get ready for school by breaking the task into smaller steps.

[advanced] Draw a flowchart to show how to prepare a simple sandwich by breaking the task into smaller steps, including a decision to add extra ingredients or not.

Practice

1. What is the main purpose of decomposition in problem solving?

easy

A. To combine many small problems into one big problem

B. To avoid solving the problem completely

C. To break a big problem into smaller, easier parts

D. To make the problem more confusing

Solution

1. Step 1: Understand the meaning of decomposition

   Decomposition means breaking down a complex problem into smaller parts.

2. Step 2: Identify the purpose of breaking down problems

   This helps make the problem easier to understand and solve step-by-step.

3. Final Answer:

   To break a big problem into smaller, easier parts -> Option C

4. Quick Check:

   Decomposition = breaking big problem into smaller parts [OK]

Hint: Think: big problem -> smaller pieces [OK]

Common Mistakes:

• Confusing decomposition with combining problems
• Thinking decomposition makes problems harder
• Believing decomposition avoids solving problems

2. Which of the following is the correct way to start decomposing a problem?

easy

A. Identify smaller tasks that make up the problem

B. Ignore the problem and guess the answer

C. Write one big solution without parts

D. Combine unrelated problems into one

Solution

1. Step 1: Understand how to begin decomposition

   Start by identifying smaller tasks or parts that together solve the big problem.

2. Step 2: Recognize the wrong approaches

   Writing one big solution or ignoring the problem does not help break it down.

3. Final Answer:

   Identify smaller tasks that make up the problem -> Option A

4. Quick Check:

   Start decomposition by finding smaller tasks [OK]

Hint: Find smaller tasks first [OK]

Common Mistakes:

• Trying to solve the whole problem at once
• Ignoring the problem instead of breaking it down
• Mixing unrelated problems

3. Look at this flowchart for making a sandwich:

Which step is an example of decomposition?

medium

A. Close sandwich

B. Eat sandwich

C. Add filling

D. Get bread

Solution

1. Step 1: Understand decomposition in the flowchart

   Decomposition breaks a big task (make sandwich) into smaller steps like getting bread, adding filling.

2. Step 2: Identify which step shows breaking down the task

   Getting bread is a smaller part of the whole sandwich-making process, so it is decomposition.

3. Final Answer:

   Get bread -> Option D

4. Quick Check:

   Decomposition = breaking task into smaller steps like 'Get bread' [OK]

Hint: Look for smaller steps in a big task [OK]

Common Mistakes:

• Choosing the final step as decomposition
• Confusing eating with breaking down tasks
• Ignoring the flowchart steps

4. A student tries to decompose the task 'clean the house' but writes only 'clean everything at once'. What is wrong with this approach?

medium

A. They did not break the task into smaller parts

B. They broke the task into too many parts

C. They solved the problem correctly

D. They ignored the task completely

Solution

1. Step 1: Analyze the student's approach

   The student wrote 'clean everything at once' which means no smaller parts were identified.

2. Step 2: Understand the importance of breaking tasks down

   Decomposition requires dividing a big task into smaller, manageable parts, which was not done here.

3. Final Answer:

   They did not break the task into smaller parts -> Option A

4. Quick Check:

   Decomposition needs smaller parts, not one big task [OK]

Hint: Break big tasks into smaller parts [OK]

Common Mistakes:

• Thinking doing everything at once is decomposition
• Believing too many parts is wrong
• Ignoring the task instead of breaking it down

5. You want to build a simple app that tracks daily water intake. Which is the best way to use decomposition to plan this app?

hard

A. Only focus on showing daily total without input or storage

B. Break the app into parts: input water amount, store data, show daily total

C. Ignore planning and start coding randomly

D. Write all code in one big block without parts

Solution

1. Step 1: Understand the app's main functions

   The app needs to get input, save data, and display totals.

2. Step 2: Apply decomposition to plan the app

   Breaking the app into these smaller parts helps organize and build it step-by-step.

3. Final Answer:

   Break the app into parts: input water amount, store data, show daily total -> Option B

4. Quick Check:

   Decompose app into input, storage, display parts [OK]

Hint: Split app into input, storage, display [OK]

Common Mistakes:

• Trying to code everything at once
• Skipping planning and decomposition
• Ignoring important app parts