Arithmetic operators - Mini Project: Build & Apply

Arithmetic Operators in C

📖 Scenario: You are helping a small shop calculate the total cost of items bought by a customer. Each item has a price, and the customer buys a certain quantity of each item.

🎯 Goal: Build a simple C program that calculates the total cost for each item using arithmetic operators and then sums all the costs to find the grand total.

📋 What You'll Learn

Create variables for item prices and quantities

Use arithmetic operators to calculate total cost per item

Sum all item totals to get the grand total

Print the grand total

💡 Why This Matters

🌍 Real World

Calculating costs and totals is common in shopping, billing, and budgeting applications.

💼 Career

Understanding arithmetic operators and printing output is essential for any programming job involving calculations.

1

Create variables for item prices and quantities

Create four variables in C: price1 with value 10, quantity1 with value 2, price2 with value 15, and quantity2 with value 3.

C

#include 

int main() {
    // Create variables price1, quantity1, price2, quantity2 with given values
    // Your code here

    return 0;
}

Hint

Use int to declare integer variables and assign the exact values given.

2

Create variables for total cost per item

Create two variables in C: total1 and total2. Use the multiplication operator * to calculate total1 as price1 * quantity1 and total2 as price2 * quantity2.

C

#include 

int main() {
    int price1 = 10;
    int quantity1 = 2;
    int price2 = 15;
    int quantity2 = 3;

    // Calculate total1 and total2 using multiplication
    // Your code here

    return 0;
}

Hint

Use the * operator to multiply price and quantity for each item.

3

Calculate the grand total

Create a variable grand_total and use the addition operator + to sum total1 and total2.

C

#include 

int main() {
    int price1 = 10;
    int quantity1 = 2;
    int price2 = 15;
    int quantity2 = 3;

    int total1 = price1 * quantity1;
    int total2 = price2 * quantity2;

    // Calculate grand_total by adding total1 and total2
    // Your code here

    return 0;
}

Hint

Use the + operator to add the two totals.

4

Print the grand total

Use printf to display the text "Grand total: " followed by the value of grand_total and a newline.

C

#include 

int main() {
    int price1 = 10;
    int quantity1 = 2;
    int price2 = 15;
    int quantity2 = 3;

    int total1 = price1 * quantity1;
    int total2 = price2 * quantity2;

    int grand_total = total1 + total2;

    // Print the grand total
    // Your code here

    return 0;
}

Hint

Use printf("Grand total: %d\n", grand_total); to print the result.

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