Arithmetic operators

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 items are left after some are used.

Splitting a bill evenly among friends.

Checking if a number is even or odd.

Syntax

C

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

Use + to add, - to subtract, * to multiply, / to divide, and % to get the remainder.

Division between integers gives an integer result (it cuts off the decimal part).

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 9 by 2, result is 4 because it drops the decimal.

C

int quotient = 9 / 2;  // quotient is 4

Finds remainder when 9 is divided by 2, which is 1.

C

int remainder = 9 % 2;  // remainder is 1

Sample Program

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

C

#include <stdio.h>

int main() {
    int a = 15, b = 4;
    printf("Addition: %d + %d = %d\n", a, b, a + b);
    printf("Subtraction: %d - %d = %d\n", a, b, a - b);
    printf("Multiplication: %d * %d = %d\n", a, b, a * b);
    printf("Division: %d / %d = %d\n", a, b, a / b);
    printf("Remainder: %d %% %d = %d\n", a, b, a % b);
    return 0;
}

Important Notes

Remember that dividing integers drops the decimal part, so 15 / 4 is 3, not 3.75.

The modulus operator % only works with integers.

Be careful not to divide by zero; it will cause an error.

Summary

Arithmetic operators let you do basic math in C.

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

Division with integers cuts off decimals, and modulus gives the remainder.

Practice

1. Which arithmetic operator in C gives the remainder of a division?

easy

A. The multiplication operator (*)

B. The division operator (/)

C. The modulus operator (%)

D. The subtraction operator (-)

Solution

1. Step 1: Understand the modulus operator

   The modulus operator (%) returns the remainder after division of two integers.

2. Step 2: Compare with other operators

   Division (/) returns the quotient, multiplication (*) multiplies, subtraction (-) subtracts.

3. Final Answer:

   The modulus operator (%) -> Option C

4. Quick Check:

   Remainder = % operator [OK]

Hint: Remainder means modulus (%) operator [OK]

Common Mistakes:

• Confusing division (/) with modulus (%)
• Thinking multiplication (*) gives remainder
• Using subtraction (-) for remainder

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

easy

A. a x b;

B. a * b;

C. a . b;

D. a & b;

Solution

1. Step 1: Recall multiplication operator in C

   The multiplication operator in C is the asterisk symbol (*).

2. Step 2: Check each option

   a * b; uses '*', which is correct. Options B, C, D use invalid symbols for multiplication.

3. Final Answer:

   a * b; -> Option B

4. Quick Check:

   Multiply with * operator [OK]

Hint: Use * for multiplication in C [OK]

Common Mistakes:

• Using 'x' instead of '*' for multiplication
• Using '.' or '&' mistakenly
• Missing semicolon at end

3. What is the output of this C code?

int a = 7, b = 3;
printf("%d", a / b);

medium

A. 1

B. 2.333333

C. 3

D. 2

Solution

1. Step 1: Understand integer division in C

   Both a and b are integers, so a / b performs integer division, which discards the decimal part.

2. Step 2: Calculate 7 / 3 using integer division

   7 divided by 3 is 2.333..., but integer division returns 2.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   Integer division truncates decimals [OK]

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

Common Mistakes:

• Expecting floating-point result
• Confusing remainder with division result
• Using wrong format specifier in printf

4. Find the error in this C code snippet:

int x = 10;
int y = 3;
int z = x / y.0;
printf("%d", z);

medium

A. Using a floating-point number in integer division

B. Incorrect format specifier in printf

C. Missing semicolon after variable declaration

D. Division by zero error

Solution

1. Step 1: Analyze the division expression

   The expression x / y.0 uses y.0 which attempts a floating-point literal but causes invalid syntax, as x and y are integers.

2. Step 2: Understand the syntax error

   Using y.0 causes a compilation error due to invalid syntax in the integer division context.

3. Final Answer:

   Using a floating-point number in integer division -> Option A

4. Quick Check:

   Integer division must use integers only [OK]

Hint: Integer division needs integer operands only [OK]

Common Mistakes:

• Thinking printf format is wrong
• Ignoring the decimal in y.0
• Assuming division by zero

5. You want to calculate the average of two integers a and b in C and get a floating-point result. Which code snippet correctly does this?

hard

A. float avg = (a + b) / 2.0;

B. float avg = (a + b) / 2;

C. int avg = (a + b) / 2.0;

D. float avg = a / b + 2;

Solution

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

   Dividing by 2 (integer) causes integer division, losing decimals. Dividing by 2.0 (double) forces floating-point division.

2. Step 2: Check each option for correct average calculation

   float avg = (a + b) / 2; does integer division then converts to float, losing decimals. float avg = (a + b) / 2.0; divides by 2.0, giving float result. int avg = (a + b) / 2.0; stores float result in int, losing decimals. float avg = a / b + 2; is incorrect formula.

3. Final Answer:

   float avg = (a + b) / 2.0; -> Option A

4. Quick Check:

   Divide by 2.0 for float average [OK]

Hint: Divide by 2.0 to get float average [OK]

Common Mistakes:

• Dividing by integer 2 causing integer division
• Storing float result in int variable
• Wrong formula for average