5th Grade ~ Divisibility Rules

This week the fifth grade students have been learning the divisibility rules. The rules helps students to know whether or not a number is divisible by by another number without actually dividing the numbers out. The is very helpful for them to use for simplifying fractions, determining the mean of a set a data, measurement conversions and many of other concepts. The rules are listed below with an example of how to apply each one.

Divisibility Rules:

Two

If the last digit is divisible by 2 then the original number is divisible by 2.

Example: 4,368

(Since 8 is divisible by two then 4,368 is divisible by 2.)

Three 

If the sum of the digits is divisible by three then the original number is divisible by 3.

Example: 495

4+9+5 = 18

(Since 18 is divisible by 3 then 495 is divisible by 3.)

Four

If the last two digits are divisible by four then the original number is divisible by 4.

Example: 4,328

(Since 28 is divisible by four then 4,328 is divisible by 4.)

Five

If the last digit is a five or a zero then the number is divisible by 5.

Example: 3,695

(Since the last digit is a 5 then 3,695 is divisible by 5.)

Six

If the number is divisible by two and three then the number is divisible by 6.

Example: 534

Is it divisible by 2? – yes because 4 is divisible by 2

Is it divisible by 3? – yes because 5+3+4=12 and 12 is divisible by 3

… so 534 is divisible by 6

Eight 

If the last three digits are divisible by eight then the original number is divisible by 8.

Example 7,328

(Since 328 is divisible by eight then 7,328 is divisible by 8.)

Nine

If the sum of the digits is divisible by nine then the original number is divisible by 9.

Example: 495

4+9+5 = 18

(Since 18 is divisible by 9 then 495 is divisible by 9.)

Ten

If the last digit is a zero then the number is divisible by 10.

Example: 4,560

(Since the last digit is a 0 then 4,560 is divisible by 10.)

The link, http://www.quia.com/mc/11125.html, is for a website that allows your student to practice matching the divisibility rule with the corresponding number.


The websites below allow for your child to practice applying the divisibility rules.
http://www.mathslice.com/ol_dvsbl.php
http://www.vectorkids.com/vkdivisible.htm