Arithmetic operators in C++

Introduction

Arithmetic operators help you do math with numbers in your program. They let you add, subtract, multiply, divide, and find remainders easily.

Calculating the total price of items in a shopping cart.

Finding the average score of a student.

Counting how many days are left until an event.

Splitting a bill evenly among friends.

Converting units, like inches to centimeters.

Syntax

C++

result = a + b;  // addition
result = a - b;  // subtraction
result = a * b;  // multiplication
result = a / b;  // division
result = a % b;  // remainder (modulus) - only for integers

Use % only with whole numbers (integers) to get the remainder.

Division with integers gives an integer result (no decimals).

Examples

Adds 5 and 3 to get 8.

C++

int sum = 5 + 3;  // sum is 8

Subtracts 4 from 10 to get 6.

C++

int diff = 10 - 4;  // diff is 6

Multiplies 7 by 2 to get 14.

C++

int product = 7 * 2;  // product is 14

Divides 20 by 4 to get 5, and finds remainder of 20 divided by 3, which is 2.

C++

int quotient = 20 / 4;  // quotient is 5
int remainder = 20 % 3;  // remainder is 2

Sample Program

This program shows how to use all the basic arithmetic operators with two numbers, 15 and 4.

C++

#include <iostream>
using namespace std;

int main() {
    int a = 15;
    int b = 4;

    cout << "a + b = " << a + b << "\n";
    cout << "a - b = " << a - b << "\n";
    cout << "a * b = " << a * b << "\n";
    cout << "a / b = " << a / b << "\n";
    cout << "a % b = " << a % b << "\n";

    return 0;
}

Important Notes

Remember that dividing two integers gives an integer result, cutting off any decimal part.

Use floating-point numbers (like float or double) if you want decimals.

The modulus operator % only works with integers, not decimals.

Summary

Arithmetic operators let you do basic math in your code.

Use +, -, *, /, and % for addition, subtraction, multiplication, division, and remainder.

Division with integers drops decimals; use floating-point types for decimal results.

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