Title: Divisibility and Mental Math
1Divisibility and Mental Math
2Vocabulary
A number is divisible by another number if it can
be divided into and result in a remainder of 0.
24 is divisible by 4, because 24 4 6. 24 is
not divisible by 5, because 24 5 4.8 (or 4R4).
An even number ends with a 0, 2, 4, 6, or 8.
An odd number ends with a 1, 3, 5, 7, or 9.
3Divisibility Rules
2 divides into all even numbers.
3 divides into a number if the sum of the digits
of that number is divisible by 3.
5 divides into numbers that end with a 5 or 0.
9 divides into a number if the sum of the digits
of that number is divisible by 9.
10 divides into numbers that end with 0.
4Example Test each number for divisibility by 3.
216
2 1 6 9
9 is divisible by 3, so 216 is divisible by 3.
yes
437
4 3 7 14
14 is not divisible by 3, so 437 is not divisible
by 3.
no
5Example Test the number for divisibility by 2,
5, or 10.
454,320
2 works because the number is even.
5 works because the number ends with 0.
10 works because the number ends with 0.
4 5 4 3 2 0 18.
Is the number divisible by 9?
18 is divisible by 9, so 454,320 is also
divisible by 9.
6Homework Time