Conditional logic (if-then decisions) in Intro to Computing - Draw & Build Visually

Draw This - beginner

Draw a flowchart to decide if a person can enter a club based on their age. The rule is: if the person is 18 years or older, they can enter; otherwise, they cannot enter.

5 minutes

Hint 1

Hint 2

Hint 3

Hint 4

Hint 5

Grading Criteria

Start and End symbols present

Input symbol used to get age

Decision diamond correctly checks 'Is Age >= 18?'

Two distinct paths for Yes and No decisions

Outputs clearly labeled 'Allow Entry' and 'Deny Entry'

Flow lines correctly connect all symbols

Solution

  _______
 /       \
|  Start  |
 \_______/
     |
     v
  ___________
 | Input Age |
  -----------
     |
     v
  _______________
 | Is Age >= 18? |
  ---------------
     |Yes          |No
     v             v
  ___________   ____________
 | Allow Entry| | Deny Entry |
  -----------   ------------
     |             |
     v             v
  _________     _________
 |  End    |   |  End    |
  ---------     ---------

This flowchart starts with the Start symbol. Then it takes the person's age as input. Next, it uses a decision diamond to check if the age is 18 or more.

If the answer is Yes, the flow goes to the Allow Entry output, then ends.

If the answer is No, the flow goes to the Deny Entry output, then ends.

This shows a simple if-then decision: if age is 18 or older, allow entry; else, deny entry.

Variations - 2 Challenges

[intermediate] Draw a flowchart to decide if a person can enter a club based on their age and membership status. Rule: If the person is 18 or older and is a member, they can enter; otherwise, they cannot enter.

[advanced] Draw a flowchart to decide ticket price based on age: if age is less than 12, price is $5; if age is between 12 and 64, price is $10; if age is 65 or older, price is $7.

Practice

1.

What does an if statement do in a program?

easy

A. It stores data in a list.

B. It repeats code multiple times.

C. It checks a condition and runs code only if the condition is true.

D. It creates a new variable.

Solution

1. Step 1: Understand the purpose of if

   An if statement asks a question that can be true or false.

2. Step 2: Identify what happens when the condition is true

   If the condition is true, the program runs the code inside the if block; otherwise, it skips it.

3. Final Answer:

   It checks a condition and runs code only if the condition is true. -> Option C

4. Quick Check:

   if = condition check [OK]

Hint: Remember: if means 'only if true' run code [OK]

Common Mistakes:

• Thinking if repeats code like a loop
• Confusing if with data storage
• Believing if creates variables

2.

Which of the following is the correct syntax for an if statement in Python?

___ x > 10:
    print("x is greater than 10")

easy

A. else

B. for

C. while

D. if

Solution

1. Step 1: Identify the keyword for condition checking

   Python uses if to start a condition check.

2. Step 2: Match the syntax with the code block

   The colon : after the condition is required to start the indented block.

3. Final Answer:

   if -> Option D

4. Quick Check:

   Python if syntax = if [OK]

Hint: If checking condition, start with 'if' keyword [OK]

Common Mistakes:

• Using 'for' or 'while' instead of 'if'
• Forgetting the colon after the condition
• Using 'else' without an 'if'

3.

What will be printed by this Python code?

age = 20
if age >= 18:
    print("Adult")
else:
    print("Child")

medium

A. Adult

B. No output

C. Child

D. Error

Solution

1. Step 1: Check the condition age >= 18

   Variable age is 20, which is greater than or equal to 18, so condition is true.

2. Step 2: Determine which block runs

   Since condition is true, the print("Adult") line runs, printing "Adult".

3. Final Answer:

   Adult -> Option A

4. Quick Check:

   20 >= 18 = Adult [OK]

Hint: Check if condition is true to pick printed output [OK]

Common Mistakes:

• Choosing 'Child' without checking condition
• Thinking no output if condition true
• Assuming syntax error

4.

Find the error in this code snippet:

if score > 50
    print("Pass")
else:
    print("Fail")

medium

A. Wrong indentation of print statements

B. Missing colon after if condition

C. Using else without if

D. Incorrect comparison operator

Solution

1. Step 1: Check syntax of if statement

   Python requires a colon : at the end of the if condition line.

2. Step 2: Identify the missing colon

   The line if score > 50 is missing the colon, causing a syntax error.

3. Final Answer:

   Missing colon after if condition -> Option B

4. Quick Check:

   Colon needed after if condition [OK]

Hint: Look for missing colon after if condition line [OK]

Common Mistakes:

• Ignoring missing colon error
• Thinking indentation is wrong here
• Confusing else usage

5.

You want to write a program that prints "Good morning" if the hour is less than 12, and "Good afternoon" otherwise. Which code correctly implements this?

hour = 10
___ hour < 12:
    print("Good morning")
else:
    print("Good afternoon")

hard

A. if

B. else if

C. elif

D. while

Solution

1. Step 1: Choose the correct keyword for the first condition

   The first condition must start with if to check if hour < 12.

2. Step 2: Use else for the alternative

   The else block runs if the if condition is false, printing "Good afternoon".

3. Final Answer:

   if -> Option A

4. Quick Check:

   Use if for first condition, else for alternative [OK]

Hint: Start conditions with if, alternatives with else [OK]

Common Mistakes:

• Using 'else if' instead of 'if' in Python
• Using 'elif' without a preceding if
• Using 'while' instead of if for decisions