Arithmetic operators in C Sharp (C#) - Mini Project: Build & Apply

Arithmetic Operators in C#

📖 Scenario: You are helping a small shop calculate prices and discounts using simple math. You will use arithmetic operators to add, subtract, multiply, and divide numbers.

🎯 Goal: Build a C# program that uses arithmetic operators to calculate the total price, discount amount, and final price after discount.

📋 What You'll Learn

Create variables with exact names and values for prices and discount rate

Use arithmetic operators +, -, *, / correctly

Print the final calculated values exactly as instructed

💡 Why This Matters

🌍 Real World

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

💼 Career

Understanding arithmetic operators is essential for any programming job that involves calculations or data processing.

1

Create initial price variables

Create two double variables called price1 and price2 with values 15.50 and 24.30 respectively.

C Sharp (C#)

# Your code here

Hint

Use double type for decimal numbers and assign the exact values.

2

Add a discount rate variable

Create a double variable called discountRate and set it to 0.10 (which means 10%).

C Sharp (C#)

double price1 = 15.50;
double price2 = 24.30;
# Your code here

Hint

Remember to use double and assign the exact value 0.10.

3

Calculate total price and discount amount

Create a double variable called totalPrice that adds price1 and price2. Then create a double variable called discountAmount that multiplies totalPrice by discountRate.

C Sharp (C#)

double price1 = 15.50;
double price2 = 24.30;
double discountRate = 0.10;
# Your code here

Hint

Use + to add prices and * to calculate discount.

4

Calculate final price and print results

Create a double variable called finalPrice that subtracts discountAmount from totalPrice. Then print totalPrice, discountAmount, and finalPrice each on its own line using Console.WriteLine.

C Sharp (C#)

double price1 = 15.50;
double price2 = 24.30;
double discountRate = 0.10;
double totalPrice = price1 + price2;
double discountAmount = totalPrice * discountRate;
# Your code here

Hint

Use - to subtract and Console.WriteLine to print each value on a new line.

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