Rules of Divisibility
Chapter 7
Rule of “2”
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If the number ends with:0, 2, 4, 6, or 8
It is divisible by 2
Divisible=Divide
Divisible means a number can go into
another number evenly with no remainder
The Rule of “2”
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Example:
48, 56, 22, 10 and 34
Are all divisible by 2
Explain why: They all end with a number
that is divisible by 2
Practice
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88, 95, 108, 2004, 26, 44
Which number is not divisible by “2”
Answer 95
Explain why?
5 is not divisible by 2
Rule of “5”
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Rule of “5”
The number must end with 5 or 0
Example: 550
Ends with 0, so it is divisible by 5
Practice
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Which numbers are divisible by 5 ?
262, 265, 360, 455 and 291
Answer:
265
360
455
Explain why?
The numbers end 5 or 0
Rule of “10”
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Rule of 10
The number has to end with 0 to be
divisible by 10
Example: 690
Ends with 0, so 690 is divisible by 10
Practice
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Which number is divisible by 10
550 or 600
Answer
Both 550 and 600
Explain why: They both end with 0
Rule of “4”
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Rule of “4”
The last two digits of a number must be
divisible by 4
Example: 444
Take the last two digits of the number 444
Divide by 4: 44÷4= 11
444 is divisible by 4
Practice
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Which number is divisible by 4
460 or 328
Answer
Both
Why?
4 can go into 28 evenly
4 can go in 60 evenly
Rule of “3”
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The sum of the digits must be divisible by 3
Example: 240
Add up each digit: 2 + 4 + 0 = 6
Now divide 6÷3=2
3 goes into 6 with no remainder so 240 is
divisible by 3
Practice
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Which number is divisivble by 3
24 or 81
Answer
Both
Why?
2 + 4=6, three goes into six evenly
8 + 1= 9 three goes into nine evenly
Rule of 9
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The sum of the digits must be divisible by 9
Example: 360
3+6+0=9
Now take the sum which is “9” and divide
9÷9=1
360 is divisible by 9
Practice
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Which number is divisible by 9?
540 or 361
Answer
540
Why 5 + 4 + 0 = 9
9 goes into 9 evenly with no remainder