Arithmetic operators - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are arithmetic operators in C?

Arithmetic operators are symbols used to perform basic math operations like addition (+), subtraction (-), multiplication (*), division (/), and modulus (%).

beginner

What does the modulus operator (%) do in C?

The modulus operator (%) gives the remainder after dividing one number by another. For example, 7 % 3 equals 1 because 7 divided by 3 leaves a remainder of 1.

intermediate

How does integer division behave in C when using the division operator (/)?

When dividing two integers, C performs integer division, which means it divides and then drops any decimal part, returning only the whole number part.

beginner

What is the result of the expression: 5 + 3 * 2 in C?

The result is 11 because multiplication (*) has higher priority than addition (+). So, 3 * 2 = 6, then 5 + 6 = 11.

beginner

Can arithmetic operators be used with floating-point numbers in C?

Yes, arithmetic operators like +, -, *, and / can be used with floating-point numbers (like float or double) to perform math with decimals.

What is the output of the expression 10 / 4 in C when both numbers are integers?

A 2

B 2.5

C 3

D 4

Integer division drops the decimal part, so 10 / 4 equals 2.

Which operator gives the remainder of a division in C?

A %

B -

C *

D +

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

What is the result of 8 + 2 * 5 in C?

A 20

B 18

C 50

D 30

Multiplication happens first: 2 * 5 = 10, then 8 + 10 = 18.

Which operator is used for multiplication in C?

A /

B -

C %

D *

The asterisk (*) is the multiplication operator.

Can you use arithmetic operators with float variables in C?

A No, only integers

B Only + and -

C Yes, for +, -, *, /

D Only * and /

Arithmetic operators +, -, *, and / work with float and double types.

Explain how the division operator (/) works differently with integers and floating-point numbers in C.

Think about dividing 7 by 2 as int and float.

Describe the order of operations when using multiple arithmetic operators in a single expression in C.

Remember PEMDAS or operator precedence.

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