Arithmetic operators in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of mixed arithmetic operations

What is the output of the following C++ code?

C++

#include <iostream>
int main() {
    int a = 5, b = 3, c = 2;
    int result = a + b * c - b / c;
    std::cout << result << std::endl;
    return 0;
}

A 9

B 10

C 11

D 8

💡 Hint

Remember the order of operations: multiplication and division before addition and subtraction.

Multiplication and division (left-to-right) happen before addition and subtraction. So b * c = 3 * 2 = 6, b / c = 3 / 2 = 1 (integer division). Then a + 6 - 1 = 5 + 6 - 1 = 10.

❓ Predict Output

intermediate

Result of integer division and modulo

What is the output of this C++ code snippet?

C++

#include <iostream>
int main() {
    int x = 17, y = 5;
    std::cout << x / y << " " << x % y << std::endl;
    return 0;
}

A 3 3

B 2 3

C 2 2

D 3 2

💡 Hint

Integer division discards the decimal part. Modulo gives the remainder.

17 divided by 5 is 3 with remainder 2. So output is '3 2'.

❓ Predict Output

advanced

Output of mixed signed and unsigned arithmetic

What is the output of this C++ code?

C++

#include <iostream>
int main() {
    int a = -3;
    unsigned int b = 2;
    std::cout << a + b << std::endl;
    return 0;
}

A 4294967295

B -1

C 0

D 1

💡 Hint

When mixing signed and unsigned, signed is converted to unsigned.

The signed int -3 is converted to unsigned int, which becomes a large number (on 32-bit unsigned, 4294967293). Adding 2 gives 4294967295.

❓ Predict Output

advanced

Result of floating point division and multiplication

What is the output of this C++ program?

C++

#include <iostream>
int main() {
    double x = 7.5, y = 2.5;
    double result = x / y * y;
    std::cout << result << std::endl;
    return 0;
}

A 7.5

B 7.499999999999999

C 10

D 2.5

💡 Hint

Floating point arithmetic can have small precision errors, but this calculation should return the original value.

7.5 / 2.5 = 3.0, then 3.0 * 2.5 = 7.5 exactly, so output is 7.5.

🧠 Conceptual

expert

Understanding operator precedence and associativity

Given the expression in C++:
int x = 4 + 3 * 2 / 6 - 1;
Which of the following shows the correct order of operations applied?

A Multiply, Add, Divide, Subtract

B Add, Multiply, Divide, Subtract

C Multiply, Divide, Add, Subtract

D Divide, Multiply, Add, Subtract

💡 Hint

Multiplication and division have the same precedence and are evaluated left to right before addition and subtraction.

Multiplication and division are done first, from left to right, then addition and subtraction. So multiply (3*2=6), divide (6/6=1), then add (4+1=5), then subtract (5-1=4).

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 meaning of each operator

   The operator % returns the remainder after division, while / returns the quotient.

2. Step 2: Identify the operator for remainder

   Since remainder is asked, the correct operator is %.

3. Final Answer:

   % -> Option C

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remainder uses % symbol, not division / [OK]

Common Mistakes:

• Confusing / with %
• Using * for remainder
• Using - for remainder

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

easy

A. a * b;

B. a x b;

C. a multiply b;

D. a . b;

Solution

1. Step 1: Recall multiplication operator syntax

   In C++, multiplication uses the asterisk symbol * between operands.

2. Step 2: Check each option

   Only a * b; uses the correct operator and syntax.

3. Final Answer:

   a * b; -> Option A

4. Quick Check:

   Multiplication operator = * [OK]

Hint: Use * for multiplication, not words or symbols [OK]

Common Mistakes:

• Using x instead of *
• Writing multiply as word
• Using dot operator for math

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

int a = 10, b = 3;
std::cout << a / b << std::endl;

medium

A. 3.33333

B. 3

C. 4

D. Error

Solution

1. Step 1: Understand integer division in C++

   Both a and b are integers, so division truncates decimals.

2. Step 2: Calculate integer division result

   10 divided by 3 is 3.333..., but integer division returns 3.

3. Final Answer:

   3 -> Option B

4. Quick Check:

   Integer division truncates decimals = 3 [OK]

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

Common Mistakes:

• Expecting decimal result
• Using floating-point division without casting
• Thinking output is error

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

int x = 5;
int y = 2;
int z = x / y.0;
std::cout << z << std::endl;

medium

A. Syntax error due to decimal point in divisor

B. Using floating-point literal with integer division

C. Incorrect variable declaration

D. Missing semicolon

Solution

1. Step 1: Analyze the divisor y.0

   The expression y.0 is invalid syntax in C++ because variables cannot have decimal points.

2. Step 2: Identify the syntax error

   The decimal point after y causes a syntax error; correct would be y * 1.0 or static_cast<double>(y).

3. Final Answer:

   Syntax error due to decimal point in divisor -> Option A

4. Quick Check:

   Variable names cannot have decimal points [OK]

Hint: Variable names can't have dots; causes syntax error [OK]

Common Mistakes:

• Thinking y.0 is valid float
• Ignoring syntax error
• Confusing variable and literal

5. Given int a = 7, b = 4;, which expression correctly calculates the average as a floating-point number in C++?

hard

A. a / b + 2

B. (a + b) / 2

C. a + b / 2

D. (a + b) / 2.0

Solution

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

   Using 2 divides integers, truncating decimals. Using 2.0 forces floating-point division.

2. Step 2: Evaluate each option

   (a + b) / 2 does integer division, result 5. (a + b) / 2.0 divides by 2.0, giving 5.5 as float. Options C and D do not calculate average correctly.

3. Final Answer:

   (a + b) / 2.0 -> Option D

4. Quick Check:

   Use floating-point divisor for decimal average [OK]

Hint: Divide by 2.0 to get decimal average, not integer [OK]

Common Mistakes:

• Using integer 2 causing truncation
• Wrong operator precedence
• Misinterpreting average formula