Math-related operations in Python - Mini Project: Build & Apply

Math-related operations

📖 Scenario: You are helping a small shop owner calculate the total cost of items bought by customers. Each item has a price, and the owner wants to know the total amount to charge.

🎯 Goal: Build a simple Python program that stores item prices, sets a discount threshold, calculates the total price of items above the threshold, and prints the final total.

📋 What You'll Learn

Create a dictionary with item names and their prices

Create a discount threshold variable

Calculate the sum of prices for items with prices above the threshold

Print the total sum

💡 Why This Matters

🌍 Real World

Shop owners and cashiers often need to calculate totals and apply discounts based on price thresholds.

💼 Career

Understanding how to work with data collections and conditions is essential for roles in data entry, retail software, and basic programming tasks.

1

Create the item prices dictionary

Create a dictionary called items with these exact entries: 'apple': 30, 'banana': 10, 'orange': 20, 'mango': 50

Python

# Create the items dictionary with prices
# Your code here

Hint

Use curly braces {} to create a dictionary with key-value pairs.

2

Set the discount threshold

Create a variable called threshold and set it to 20

Python

items = {'apple': 30, 'banana': 10, 'orange': 20, 'mango': 50}
# Set the discount threshold
# Your code here

Hint

Just assign the number 20 to the variable named threshold.

3

Calculate total price above threshold

Create a variable called total and use a for loop with variables item and price to iterate over items.items(). Add price to total only if price is greater than threshold

Python

items = {'apple': 30, 'banana': 10, 'orange': 20, 'mango': 50}
threshold = 20
# Calculate total price of items with price above threshold
# Your code here

Hint

Start total at 0. Use a for loop to check each price. Add price to total only if it is greater than threshold.

4

Print the total price

Write a print statement to display the value of total

Python

items = {'apple': 30, 'banana': 10, 'orange': 20, 'mango': 50}
threshold = 20
total = 0
for item, price in items.items():
    if price > threshold:
        total += price
# Print the total price
# Your code here

Hint

Use print(total) to show the final sum.

Practice

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

easy

A. The multiplication operator *

B. The division operator /

C. The exponent operator **

D. The modulus operator %

Solution

1. Step 1: Understand the modulus operator

   The modulus operator % returns the remainder after division of one number by another.

2. Step 2: Compare with other operators

   The division operator / returns the quotient, exponent ** raises to power, and multiplication * multiplies numbers.

3. Final Answer:

   The modulus operator % -> Option D

4. Quick Check:

   Remainder = % operator [OK]

Hint: Remainder uses % operator in math [OK]

Common Mistakes:

• Confusing / with %
• Using * for remainder
• Thinking ** gives remainder

2. Which of the following is the correct operator syntax to calculate 3 to the power of 4 in Python?

easy

A. 3 ^ 4

B. 3 ^^ 4

C. 3 ** 4

D. pow(3, 4)

Solution

1. Step 1: Identify the exponent operator in Python

   Python uses ** to calculate powers, so 3 ** 4 means 3 to the power 4.

2. Step 2: Check other options

   3 ^ 4 is bitwise XOR, pow(3, 4) is a function but not syntax operator, 3 ^^ 4 is invalid syntax.

3. Final Answer:

   3 ** 4 -> Option C

4. Quick Check:

   Power uses ** operator [OK]

Hint: Use ** for powers, not ^ [OK]

Common Mistakes:

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

3. What is the output of this Python code?

result = 10 % 3
print(result)

medium

A. 1

B. 3

C. 0

D. 10

Solution

1. Step 1: Calculate 10 modulo 3

   10 divided by 3 is 3 with remainder 1, so 10 % 3 equals 1.

2. Step 2: Understand print output

   The print statement outputs the value stored in result, which is 1.

3. Final Answer:

   1 -> Option A

4. Quick Check:

   10 % 3 = 1 [OK]

Hint: Modulo gives remainder after division [OK]

Common Mistakes:

• Confusing modulo with division
• Expecting quotient instead of remainder
• Misreading print output

4. Find the error in this code snippet:

value = 5 **
print(value)

medium

A. print() function is used incorrectly

B. Missing second operand for exponent operator

C. Exponent operator should be ^

D. Variable name 'value' is invalid

Solution

1. Step 1: Check the exponent operator usage

   The exponent operator ** needs two numbers, but here only one number (5) is given before it.

2. Step 2: Identify syntax error

   Because the second operand is missing, Python will raise a syntax error before print runs.

3. Final Answer:

   Missing second operand for exponent operator -> Option B

4. Quick Check:

   ** needs two numbers [OK]

Hint: Exponent needs two numbers, not one [OK]

Common Mistakes:

• Using ^ instead of **
• Thinking print() is wrong here
• Assuming variable name causes error

5. You want to calculate the area of a circle with radius 7 using Python. Which code correctly uses math operations to do this?

import math
radius = 7
area = ?
print(area)

hard

A. area = math.pi * (radius ** 2)

B. area = math.pi ** radius

C. area = pi * radius * radius

D. area = math.pi + radius ** 2

Solution

1. Step 1: Recall formula for circle area

   The area of a circle is π times radius squared, or π * r².

2. Step 2: Translate formula to Python code

   Use math.pi for π and radius ** 2 for radius squared, so math.pi * (radius ** 2).

3. Final Answer:

   area = math.pi * (radius ** 2) -> Option A

4. Quick Check:

   Area = π * r² [OK]

Hint: Use ** 2 for square, multiply by math.pi [OK]

Common Mistakes:

• Using addition instead of multiplication
• Using exponent on pi instead of radius
• Forgetting to square radius