How to Use Arithmetic Operators in Ruby: Simple Guide

In Ruby, you use +, -, *, /, and % to perform addition, subtraction, multiplication, division, and modulus operations respectively. These operators work directly with numbers to calculate and return results.

Syntax

Ruby uses simple symbols for arithmetic operations:

• + for addition
• - for subtraction
• * for multiplication
• / for division
• % for modulus (remainder)

You write expressions by placing these operators between numbers or variables.

ruby

result = 5 + 3
result = 10 - 4
result = 6 * 7
result = 20 / 5
result = 10 % 3

Example

This example shows how to use each arithmetic operator and print the result.

ruby

a = 15
b = 4
puts "Addition: #{a + b}"
puts "Subtraction: #{a - b}"
puts "Multiplication: #{a * b}"
puts "Division: #{a / b}"
puts "Modulus: #{a % b}"

Output

Addition: 19
Subtraction: 11
Multiplication: 60
Division: 3
Modulus: 3

Common Pitfalls

One common mistake is integer division returning an integer instead of a decimal. For example, 5 / 2 returns 2, not 2.5. To get a decimal, use floating-point numbers like 5.0 / 2.

Also, avoid dividing by zero as it causes an error.

ruby

puts 5 / 2       # Outputs 2 (integer division)
puts 5.0 / 2     # Outputs 2.5 (floating-point division)

# Wrong: division by zero
# puts 5 / 0      # Raises ZeroDivisionError

# Right: check before dividing
if b != 0
  puts a / b
else
  puts "Cannot divide by zero"
end

Output

2
2.5
Cannot divide by zero

Quick Reference

Operator	Meaning	Example	Result
+	Addition	3 + 2	5
-	Subtraction	5 - 1	4
*	Multiplication	4 * 3	12
/	Division	10 / 2	5
%	Modulus (remainder)	10 % 3	1

Key Takeaways

Use +, -, *, /, and % for basic arithmetic in Ruby.

Division with integers returns an integer; use floats for decimals.

Avoid dividing by zero to prevent errors.

Arithmetic operators work directly with numbers and variables.

Use string interpolation to display results clearly.