Arithmetic operators in Python - Mini Project: Build & Apply

Arithmetic Operators Practice

📖 Scenario: You are helping a small shop owner calculate prices and discounts for items sold.

🎯 Goal: Build a simple program that uses arithmetic operators to calculate the total price, discount amount, and final price after discount.

📋 What You'll Learn

Create variables for item price and quantity

Create a variable for discount rate

Calculate total price using multiplication

Calculate discount amount using multiplication

Calculate final price by subtracting discount from total price

Print the final price

💡 Why This Matters

🌍 Real World

Calculating prices and discounts is common in shopping and billing systems.

💼 Career

Understanding arithmetic operators is essential for programming tasks involving calculations, finance, and data processing.

1

Create item price and quantity variables

Create a variable called item_price and set it to 20. Create another variable called quantity and set it to 3.

Python

# Create variables item_price and quantity with values 20 and 3
# Your code here

Hint

Use the assignment operator = to set values.

2

Create discount rate variable

Create a variable called discount_rate and set it to 0.1 (which means 10%).

Python

item_price = 20
quantity = 3
# Create variable discount_rate with value 0.1
# Your code here

Hint

Remember that 10% as a decimal is 0.1.

3

Calculate total price, discount amount, and final price

Calculate the total price by multiplying item_price and quantity and store it in total_price. Calculate the discount amount by multiplying total_price and discount_rate and store it in discount_amount. Calculate the final price by subtracting discount_amount from total_price and store it in final_price.

Python

item_price = 20
quantity = 3
discount_rate = 0.1
# Calculate total_price, discount_amount, and final_price
# Your code here

Hint

Use * for multiplication and - for subtraction.

4

Print the final price

Write a print statement to display the value of final_price.

Python

item_price = 20
quantity = 3
discount_rate = 0.1
total_price = item_price * quantity
discount_amount = total_price * discount_rate
final_price = total_price - discount_amount
# Print the final_price
# Your code here

Hint

Use print(final_price) to show the result.

Practice

1. Which arithmetic operator in Python is used to find the remainder of a division?

easy

A. **

B. //

C. %

D. +

Solution

1. Step 1: Understand the meaning of each operator

   The operator % gives the remainder after division, // gives the floor division result, ** is for power, and + is for addition.

2. Step 2: Identify the operator for remainder

   The remainder operator is %, which returns the leftover part after dividing two numbers.

3. Final Answer:

   % -> Option C

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remainder operator looks like a percent sign % [OK]

Common Mistakes:

• Confusing // (floor division) with %
• Using ** instead of %
• Thinking + gives remainder

2. Which of the following is the correct operator syntax to calculate 5 to the power of 3 in Python?

easy

A. 5 ^ 3

B. pow(5, 3)

C. 5 ^^ 3

D. 5 ** 3

Solution

1. Step 1: Recall Python's power operator syntax

   Python uses ** to calculate powers, so 5 ** 3 means 5 to the power of 3.

2. Step 2: Check other options for correctness

   5 ^ 3 is bitwise XOR, 5 ^^ 3 is invalid syntax, and pow(5, 3) is a function call but not an operator syntax.

3. Final Answer:

   5 ** 3 -> Option D

4. Quick Check:

   Power operator = ** [OK]

Hint: Use ** for power, not ^ or ^^ [OK]

Common Mistakes:

• Using ^ instead of ** for power
• Trying ^^ which is invalid
• Confusing function pow() with operator syntax

3. What is the output of the following code?

result = 17 // 4
print(result)

medium

A. 4.25

B. 4

C. 1

D. Error

Solution

1. Step 1: Understand floor division operator //

   The operator // divides and returns the largest whole number less than or equal to the result.

2. Step 2: Calculate 17 // 4

   17 divided by 4 is 4.25, floor division drops the decimal part, so result is 4.

3. Final Answer:

   4 -> Option B

4. Quick Check:

   17 // 4 = 4 [OK]

Hint: Floor division drops decimals, so 17//4 is 4 [OK]

Common Mistakes:

• Confusing // with / which gives float
• Expecting 4.25 instead of 4
• Thinking // rounds up

4. Find the error in this code snippet:

num = 10
result = num % 0
print(result)

medium

A. ZeroDivisionError at runtime

B. No error, output is 0

C. SyntaxError due to % operator

D. TypeError because 0 is int

Solution

1. Step 1: Understand modulo operator with zero

   The modulo operator % cannot divide by zero; it causes an error.

2. Step 2: Identify the error type

   Dividing or modulo by zero raises a ZeroDivisionError at runtime.

3. Final Answer:

   ZeroDivisionError at runtime -> Option A

4. Quick Check:

   Modulo by zero causes ZeroDivisionError [OK]

Hint: Modulo by zero causes runtime error, never allowed [OK]

Common Mistakes:

• Thinking it causes syntax error
• Expecting output 0 instead of error
• Confusing with TypeError

5. You want to calculate the area of a square with side length stored in variable side. Which expression correctly uses arithmetic operators to do this?

hard

A. area = side ** 2

B. area = side // 2

C. area = side + side

D. area = side * 2

Solution

1. Step 1: Recall formula for square area

   The area of a square is side length multiplied by itself, or side squared.

2. Step 2: Match formula with operators

   Using side ** 2 calculates side to the power of 2, which is correct for area.

3. Final Answer:

   area = side ** 2 -> Option A

4. Quick Check:

   Square area = side squared = side ** 2 [OK]

Hint: Square area = side squared, use ** 2 [OK]

Common Mistakes:

• Using side * 2 which doubles side, not area
• Using side + side which adds sides, not area
• Using floor division // which is incorrect