Conditional logic (if-then decisions) in Intro to Computing - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ trace

intermediate

Trace the output of nested if-else statements

Consider the following code snippet. What will be the output after running it?

score = 75
if score >= 90:
    result = "Excellent"
elif score >= 70:
    result = "Good"
else:
    result = "Needs Improvement"
print(result)

Intro to Computing

score = 75
if score >= 90:
    result = "Excellent"
elif score >= 70:
    result = "Good"
else:
    result = "Needs Improvement"
print(result)

A Excellent

B No output (error)

C Needs Improvement

D Good

💡 Hint

Check which condition the score 75 satisfies first.

The score 75 is not >= 90, so the first if is false. The elif checks if score >= 70, which is true, so result is set to "Good". The else block is skipped.

🧠 Conceptual

intermediate

Identify the role of else in conditional statements

Which of the following best describes the role of the else block in an if-then decision structure?

A It runs only if the if condition is false and no elif conditions are true.

B It runs regardless of the if condition.

C It runs only if the if condition is true.

D It runs only if all conditions are true.

💡 Hint

Think about when else executes compared to if and elif.

The else block runs only when none of the previous if or elif conditions are true.

❓ Comparison

advanced

Compare two conditional expressions

Which option correctly shows two equivalent ways to check if a number is between 10 and 20 inclusive?

A 10 <= num <= 20 and num > 10 and num < 20

B 10 <= num <= 20

C num > 10 or num < 20

D num >= 10 and num <= 20 and 10 < num < 20

💡 Hint

Look for the simplest and correct way to check the range.

Option B uses Python's chained comparison which is concise and correct. Other options either add redundant checks or use incorrect logic.

❓ identification

advanced

Identify the error in conditional syntax

What error will this code produce?

if x > 10
    print("Greater")
else:
    print("Smaller or equal")

Intro to Computing

if x > 10
    print("Greater")
else:
    print("Smaller or equal")

A IndentationError due to wrong indentation

B NameError because x is undefined

C SyntaxError due to missing colon after if condition

D No error, prints output correctly

💡 Hint

Check punctuation after the if condition.

Python requires a colon ':' after the if condition. Missing it causes SyntaxError.

🚀 Application

expert

Determine the final value after multiple conditions

Given the code below, what is the final value of status?

value = 15
if value > 20:
    status = "High"
elif value > 10:
    if value % 2 == 0:
        status = "Medium Even"
    else:
        status = "Medium Odd"
else:
    status = "Low"
print(status)

Intro to Computing

value = 15
if value > 20:
    status = "High"
elif value > 10:
    if value % 2 == 0:
        status = "Medium Even"
    else:
        status = "Medium Odd"
else:
    status = "Low"
print(status)

A Medium Odd

B Medium Even

C Low

D High

💡 Hint

Check the value against each condition and the inner if for even or odd.

Value 15 is not > 20, so first if is false. It is > 10, so the elif block runs. Inside, 15 % 2 is 1 (odd), so status is set to "Medium Odd".

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