Arithmetic operators in Kotlin

Introduction

Arithmetic operators help you do math with numbers in your program. They let you add, subtract, multiply, and divide values easily.

Calculating the total price of items in a shopping cart.

Finding the average score of a student.

Increasing or decreasing a counter in a game.

Converting units, like kilometers to miles.

Splitting a bill evenly among friends.

Syntax

Kotlin

val sum = a + b
val difference = a - b
val product = a * b
val quotient = a / b
val remainder = a % b

Use + for addition, - for subtraction, * for multiplication, / for division, and % for remainder (modulus).

Make sure the variables used are numbers like Int or Double.

Examples

Adds 10 and 3, then prints 13.

Kotlin

val a = 10
val b = 3
val sum = a + b
println(sum)

Finds the remainder when 10 is divided by 3, which is 1.

Kotlin

val a = 10
val b = 3
val remainder = a % b
println(remainder)

Multiplies two decimal numbers and prints 11.0.

Kotlin

val a = 5.5
val b = 2.0
val product = a * b
println(product)

Sample Program

This program shows all basic arithmetic operations with two numbers and prints the results.

Kotlin

fun main() {
    val x = 15
    val y = 4

    val sum = x + y
    val difference = x - y
    val product = x * y
    val quotient = x / y
    val remainder = x % y

    println("Sum: $sum")
    println("Difference: $difference")
    println("Product: $product")
    println("Quotient: $quotient")
    println("Remainder: $remainder")
}

Important Notes

Division between two integers returns an integer result (it cuts off decimals).

Use Double or Float types if you want decimal results from division.

The remainder operator (%) gives the leftover part after division.

Summary

Arithmetic operators let you do basic math in Kotlin.

Use +, -, *, /, and % for addition, subtraction, multiplication, division, and remainder.

Integer division drops decimals; use floating-point numbers for precise division.

Practice

1. Which arithmetic operator in Kotlin is used to find the remainder of a division?

easy

A. The / operator

B. The % operator

C. The * operator

D. The - operator

Solution

1. Step 1: Understand the meaning of each operator

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

2. Step 2: Identify the operator for remainder

   The % operator is specifically for remainder calculation in Kotlin.

3. Final Answer:

   The % operator -> Option B

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remember % means remainder in math and Kotlin [OK]

Common Mistakes:

• Confusing / with %, thinking / gives remainder
• Using * or - for remainder
• Mixing up operators with similar symbols

2. Which of the following is the correct way to write a multiplication operation in Kotlin?

easy

A. val result = 5 x 3

B. val result = 5 . 3

C. val result = 5 / 3

D. val result = 5 * 3

Solution

1. Step 1: Recall Kotlin syntax for multiplication

   Kotlin uses * for multiplication, not x or dot.

2. Step 2: Check each option

   val result = 5 * 3 uses * correctly; others are invalid syntax or different operations.

3. Final Answer:

   val result = 5 * 3 -> Option D

4. Quick Check:

   Multiplication operator = * [OK]

Hint: Use * for multiplication, not x or dot [OK]

Common Mistakes:

• Using x instead of *
• Using dot for multiplication
• Confusing division / with multiplication

3. What is the output of the following Kotlin code?

val a = 10
val b = 3
println(a / b)

medium

A. 3

B. 3.3333333

C. 3.0

D. Error

Solution

1. Step 1: Identify variable types and operation

   a and b are integers, so a / b does integer division.

2. Step 2: Calculate integer division result

   10 divided by 3 is 3.333..., but integer division drops decimals, so result is 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Integer division drops decimals = 3 [OK]

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

Common Mistakes:

• Expecting decimal result with integer division
• Confusing / with floating-point division
• Thinking output is 3.0 or error

4. The following Kotlin code has an error. What is the problem?

val x = 7
val y = 2
val result = x / y.toDouble()
println(result)

medium

A. Cannot call toDouble() on y

B. Division operator / cannot mix Int and Double

C. No error, code runs and prints 3.5

D. Missing explicit type declaration for result

Solution

1. Step 1: Analyze the types involved in division

   y.toDouble() converts y to Double, so x / y.toDouble() divides Int by Double.

2. Step 2: Check Kotlin's handling of mixed numeric types

   Kotlin automatically converts Int to Double for mixed operations, so no error occurs.

3. Final Answer:

   No error, code runs and prints 3.5 -> Option C

4. Quick Check:

   Mixed Int/Double division allowed = 3.5 [OK]

Hint: Kotlin auto-converts Int to Double in mixed division [OK]

Common Mistakes:

• Thinking toDouble() causes error
• Believing mixed types cause syntax error
• Expecting need for explicit type declaration

5. You want to calculate the average of three large integer scores (e.g., 1000000000 each) in Kotlin and get a precise decimal result. Which code snippet correctly does this?

hard

A. val avg = (score1.toDouble() + score2.toDouble() + score3.toDouble()) / 3

B. val avg = (score1 + score2 + score3) / 3.0

C. val avg = (score1 + score2 + score3).toDouble() / 3

D. val avg = (score1 + score2 + score3) / 3

Solution

1. Step 1: Understand integer division problem

   Dividing integers by integer 3 causes integer division, losing decimals.

2. Step 2: Convert all scores to Double before division

   Converting each score to Double ensures floating-point division and precise average.

3. Step 3: Check each option

   val avg = (score1.toDouble() + score2.toDouble() + score3.toDouble()) / 3 converts all scores to Double before adding and dividing, giving correct decimal average.

4. Final Answer:

   val avg = (score1.toDouble() + score2.toDouble() + score3.toDouble()) / 3 -> Option A

5. Quick Check:

   Convert all to Double before division for decimal average [OK]

Hint: Convert all integers to Double before dividing for decimals [OK]

Common Mistakes:

• Dividing integers directly causing integer division
• Converting sum to Double after integer division
• Converting only one score to Double