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Ruby Numbers

Numbers in Ruby are values used for counting and maths. Ruby works with whole numbers and with numbers that have a decimal point.

Integers and floats

An integer is a whole number with no decimal point. A float is a number with a decimal point.

puts 17
puts 2.5

Two kinds of division

Dividing two integers drops the fraction part. Making one value a float keeps the fraction part.

puts 7 / 2
puts 7.0 / 2

Remainders and negative division

The % sign finds what is left after division. Division with a negative integer rounds down to the lower whole number.

puts 7 % 2
puts -7 % 2
puts -7 / 2

Floats up close

Floats hold decimal values in a close stored form. Adding 0.1 and 0.2 shows the small gap.

puts 0.1 + 0.2

Big numbers with underscores

Underscores split a long number into groups. The printed value has no underscores.

puts 1_000_000

Example

puts 12 + 8
puts 7 / 2
puts 7.0 / 2
puts 10 % 3
puts 1_500 + 500

Key points

  • Use + to add, - to take away, * to multiply and / to divide.
  • Integer division drops the fraction part of the answer.
  • Float division keeps the fraction part of the answer.
  • The % sign gives the remainder after a division.
  • Negative integer division rounds the answer down.
  • Underscores can split a long number into groups that are easy to read.

In this example, the first line adds 12 and 8 and prints 20. The second line divides two integers and prints 3. The third line divides with a float and prints 3.5. The fourth line prints the remainder of 10 divided by 3. The last line adds two grouped numbers and prints 2000.

Note

A float keeps a close stored value, not an exact decimal value.

Try it Yourself

Edit the code, then press Run.

Running is simulated

Exercise

What does puts 7 / 2 print?