Arithmetic operators in C++ - Mini Project: Build & Apply

Arithmetic Operators Practice

📖 Scenario: You are helping a small shop calculate the total cost of items bought by a customer. You will use arithmetic operators to add, subtract, multiply, and divide numbers.

🎯 Goal: Build a simple C++ program that creates variables for item prices and quantities, calculates the total cost using arithmetic operators, and prints the result.

📋 What You'll Learn

Create variables for item prices and quantities

Create a variable for tax rate

Calculate total cost using arithmetic operators

Print the final total cost

💡 Why This Matters

🌍 Real World

Calculating prices and totals is common in shopping apps, billing systems, and financial software.

💼 Career

Understanding arithmetic operators and printing output is essential for any programming job involving calculations or data display.

1

Create item price and quantity variables

Create two double variables called price and quantity with values 5.99 and 3 respectively.

C++

#include 

int main() {
    // Create double variables price and quantity with values 5.99 and 3
    // Your code here

    return 0;
}

Hint

Use double type for decimal numbers. Assign the exact values given.

2

Add a tax rate variable

Add a double variable called tax_rate and set it to 0.07 to represent 7% tax.

C++

#include 

int main() {
    double price = 5.99;
    double quantity = 3;
    // Create double variable tax_rate with value 0.07
    // Your code here

    return 0;
}

Hint

Tax rate is a decimal number, so use double type.

3

Calculate total cost including tax

Create a double variable called total_cost that calculates the total price by multiplying price and quantity, then adding tax using tax_rate.

C++

#include 

int main() {
    double price = 5.99;
    double quantity = 3;
    double tax_rate = 0.07;
    // Calculate total_cost = price * quantity + (price * quantity * tax_rate)
    // Your code here

    return 0;
}

Hint

Multiply price and quantity first, then add tax by multiplying with tax_rate.

4

Print the total cost

Use std::cout to print the text Total cost: followed by the value of total_cost.

C++

#include 

int main() {
    double price = 5.99;
    double quantity = 3;
    double tax_rate = 0.07;
    double total_cost = price * quantity + (price * quantity * tax_rate);
    // Print Total cost: followed by total_cost
    // Your code here

    return 0;
}

Hint

Use std::cout with << to print text and variables. End with std::endl.

Practice

1. Which arithmetic operator in C++ 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 % returns the remainder after division, while / returns the quotient.

2. Step 2: Identify the operator for remainder

   Since remainder is asked, the correct operator is %.

3. Final Answer:

   % -> Option C

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remainder uses % symbol, not division / [OK]

Common Mistakes:

• Confusing / with %
• Using * for remainder
• Using - for remainder

2. Which of the following is the correct syntax to multiply two integers a and b in C++?

easy

A. a * b;

B. a x b;

C. a multiply b;

D. a . b;

Solution

1. Step 1: Recall multiplication operator syntax

   In C++, multiplication uses the asterisk symbol * between operands.

2. Step 2: Check each option

   Only a * b; uses the correct operator and syntax.

3. Final Answer:

   a * b; -> Option A

4. Quick Check:

   Multiplication operator = * [OK]

Hint: Use * for multiplication, not words or symbols [OK]

Common Mistakes:

• Using x instead of *
• Writing multiply as word
• Using dot operator for math

3. What is the output of the following C++ code?

int a = 10, b = 3;
std::cout << a / b << std::endl;

medium

A. 3.33333

B. 3

C. 4

D. Error

Solution

1. Step 1: Understand integer division in C++

   Both a and b are integers, so division truncates decimals.

2. Step 2: Calculate integer division result

   10 divided by 3 is 3.333..., but integer division returns 3.

3. Final Answer:

   3 -> Option B

4. Quick Check:

   Integer division truncates decimals = 3 [OK]

Hint: Integer division drops decimals, result is integer [OK]

Common Mistakes:

• Expecting decimal result
• Using floating-point division without casting
• Thinking output is error

4. Identify the error in this C++ code snippet:

int x = 5;
int y = 2;
int z = x / y.0;
std::cout << z << std::endl;

medium

A. Syntax error due to decimal point in divisor

B. Using floating-point literal with integer division

C. Incorrect variable declaration

D. Missing semicolon

Solution

1. Step 1: Analyze the divisor y.0

   The expression y.0 is invalid syntax in C++ because variables cannot have decimal points.

2. Step 2: Identify the syntax error

   The decimal point after y causes a syntax error; correct would be y * 1.0 or static_cast<double>(y).

3. Final Answer:

   Syntax error due to decimal point in divisor -> Option A

4. Quick Check:

   Variable names cannot have decimal points [OK]

Hint: Variable names can't have dots; causes syntax error [OK]

Common Mistakes:

• Thinking y.0 is valid float
• Ignoring syntax error
• Confusing variable and literal

5. Given int a = 7, b = 4;, which expression correctly calculates the average as a floating-point number in C++?

hard

A. a / b + 2

B. (a + b) / 2

C. a + b / 2

D. (a + b) / 2.0

Solution

1. Step 1: Understand integer vs floating-point division

   Using 2 divides integers, truncating decimals. Using 2.0 forces floating-point division.

2. Step 2: Evaluate each option

   (a + b) / 2 does integer division, result 5. (a + b) / 2.0 divides by 2.0, giving 5.5 as float. Options C and D do not calculate average correctly.

3. Final Answer:

   (a + b) / 2.0 -> Option D

4. Quick Check:

   Use floating-point divisor for decimal average [OK]

Hint: Divide by 2.0 to get decimal average, not integer [OK]

Common Mistakes:

• Using integer 2 causing truncation
• Wrong operator precedence
• Misinterpreting average formula