In Ruby there are a variety of build in methods you can perform on numbers.

• Use .even? to check whether or not an integer is even.

15.even?
4.even?
# returns:
false
true

• Use .odd? to check whether or not an integer is odd.

15.odd?
4.odd?
# returns:
true
false

• The .ceil method rounds up to the nearest integers.

8.3.ceil
6.7.ceil
# returns:
9
7

• The .floor method rounds down to the nearest integers.

8.3.floor
6.7.floor
# returns:
8
6

• Use .next to return the next consecutive integer.

15.next
2.next
-4.next
# returns:
16
3
-3

• The .to_s method changes an integer into a string.

15.to_s
# returns:
"15"

• The .gcd method returns the greatest common denominator of two numbers.

15.gcd(5)
9.gcd(4)
# returns:
5
1