Arithmetic operators in C Sharp (C#) - 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?

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.

beginner

How does integer division behave in C#?

When you divide two integers, C# returns the whole number part only, dropping any decimal. For example, 7 / 3 equals 2, not 2.333.

intermediate

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

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

beginner

Explain the difference between / and % operators in C#.

The / operator divides two numbers and returns the quotient (the result of division). The % operator returns the remainder left after division. For example, 10 / 3 is 3, and 10 % 3 is 1.

What is the output of: int result = 10 / 4; Console.WriteLine(result); ?

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 % operator returns the remainder after division.

What is the result of: 8 + 2 * 5?

A 20

B 18

C 50

D 30

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

Which operator is used for multiplication in C#?

A *

B /

C +

D -

The * symbol is used for multiplication.

What will be the output of: Console.WriteLine(15 % 4); ?

A 1

B 4

C 3

D 15

15 divided by 4 leaves a remainder of 3, so 15 % 4 is 3.

Describe the main arithmetic operators in C# and give a simple example for each.

Think about +, -, *, /, and % symbols.

Explain how operator precedence affects the result of arithmetic expressions in C#.

Consider how 5 + 3 * 2 is calculated.

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 purpose of each operator

   The % operator returns the remainder after division, while / divides, * multiplies, and - subtracts.

2. Step 2: Identify the operator for remainder

   The operator that gives the remainder is %.

3. Final Answer:

   % -> Option D

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remainder uses % symbol, like dividing candies leftover [OK]

Common Mistakes:

• Confusing / (division) with % (remainder)
• Using * or - instead of %
• Thinking % is modulus function

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

easy

A. int result = a + b;

B. int result = a * b;

C. int result = a & b;

D. int result = a x b;

Solution

1. Step 1: Recall multiplication operator in C#

   Multiplication uses the asterisk symbol * between operands.

2. Step 2: Check each option's syntax

   int result = a * b; uses * correctly. int result = a x b; uses x which is invalid. int result = a & b; uses & which is bitwise AND, not multiplication. int result = a + b; uses + which is addition.

3. Final Answer:

   int result = a * b; -> Option B

4. Quick Check:

   Multiplication operator = * [OK]

Hint: Use * for multiply, not x or & [OK]

Common Mistakes:

• Using x instead of *
• Using & thinking it's multiply
• Confusing + with *

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

int a = 7;
int b = 3;
Console.WriteLine(a / b);

medium

A. 2

B. 2.3333333

C. 3

D. 1

Solution

1. Step 1: Understand integer division in C#

   Both a and b are integers, so division a / b performs integer division, dropping decimals.

2. Step 2: Calculate integer division result

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

3. Final Answer:

   2 -> Option A

4. Quick Check:

   Integer division truncates decimals = 2 [OK]

Hint: Integer division drops decimals, so 7/3 = 2 [OK]

Common Mistakes:

• Expecting decimal result
• Confusing integer division with float division
• Using wrong operator

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

int x = 10;
int y = 0;
int z = x / y;
Console.WriteLine(z);

medium

A. Variable z is not declared

B. Missing semicolon after Console.WriteLine

C. Division by zero causes runtime error

D. x and y must be floats for division

Solution

1. Step 1: Analyze division operation

   The code divides x by y, where y is zero.

2. Step 2: Understand division by zero in C#

   Dividing an integer by zero causes a runtime error (DivideByZeroException).

3. Final Answer:

   Division by zero causes runtime error -> Option C

4. Quick Check:

   Division by zero throws error [OK]

Hint: Never divide by zero; it crashes your program [OK]

Common Mistakes:

• Ignoring division by zero error
• Thinking missing semicolon causes error
• Assuming float needed for division

5. You want to calculate the average of two integers a and b in C#. Which expression correctly computes the average as a floating-point number?

hard

A. (a + b) / 2.0

B. (a + b) / 2

C. a / 2 + b / 2

D. (float)((a + b) / 2)

Solution

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

   Using only integers causes integer division, dropping decimals.

2. Step 2: Check each option for floating-point division

   (a + b) / 2 divides integers, result is integer. (a + b) / 2.0 divides by 2.0 (double), so result is floating-point. a / 2 + b / 2 divides separately then adds, but integer division truncates each part. (float)((a + b) / 2) first performs integer division (a + b) / 2 truncating to integer, then casts to float, resulting in incorrect average due to truncation.

3. Final Answer:

   (a + b) / 2.0 -> Option A

4. Quick Check:

   Divide by 2.0 for float average [OK]

Hint: Divide by 2.0 (double) to get float average, not int [OK]

Common Mistakes:

• Using integer division dropping decimals
• Adding halves separately causing truncation
• Casting after division instead of before