2. divisibility rules - livingston public schools. divisability...2. divisibility rules september...
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2. Divisibility Rules September 04, 2015
Warm Up 94151. Name the even prime numbers from 125.
2. How do I know a number is prime?
3. How can I tell a number is divisible by 5?
4. What is something fun you are doing this Labor Day Weekend?
Divisibility Rules2, 3, 4, 5, 6, 7, 8, 9, 10
Definition of Divisibility:
able to be divided with no remainder 5 1245 5 36712
10
24
4
2045
9
450
5
Work the two problems at your desk. When you are finished we will check them for accuracy.
One of the problems divided evenly and the other has a remainder.
7
35
17
3
1521
4
20R. 1
5
The rule of....
If the last digit in a number is 0, the number will be evenly divisible by 10.
The rule of....
If the last digit in a number is 0 or 5, the number will be evenly divisible by 5.
2. Divisibility Rules September 04, 2015
The rule of....
Every even number is evenly divisible by 2.
Even numbers are numbers that end in 0, 2, 4, 6, or 8
The rule of....
A number is evenly divisible by 3 if the sum of all the digits is a multiple of 3.
Example
2,052
4,103
Reasoning
The sum of the digits is 92+0+5+2=9 Therefore, 2,052 is evenly divisible by 3
The sum of the digits is 84+1+0+3=8Therefore, 4,103 is not evenly divisible by 3
The rule of....
If the number is evenly divisible by both 2 and 3, it will also be divisible by 6.
The rule of....
If the last two digits are a multiple of 4, the number is evenly divisible by four.
240
375
240
375
4 goes into 40 so 240 is evenly divisible by four.
4 does not go into 75 so 375 is not evenly divisible by four.
Is it divisible by four?
The rule of....
Double the last digit and subtract that answer from the remaining digits. If this difference is a multiple of 7, the number is evenly divisible by 7.
683
672
Example
The last digit is a 2. Doubling 2 is the same as saying 2 x 2 which is 4. subtracting 4 from 67 gives you a difference of 63 which is a multiple of 7. Therefore, 672 is evenly divisible by 7.
The last digit is a 3. Doubling 3 is the same as saying 3 x 2 which is 6. subtracting 6 from 68 gives you a difference of 62 which is NOT a multiple of 7. Therefore, 683 is NOT evenly divisible by 7.
Applying this rule to numbers with more than 3 digits can be complicated. However, if your number has more than 3 digits, you would repeat the entire process until you reach a difference with no more than two digits.
The rule of....
If the last three digits are evenly divisible by 8, then the entire number is divisible by eight. Yes, this rule requires division.
Example
7016
6473 If you divide 016 by 8 you get a quotient of 2 with no remainder so 7, 016 is evenly divisible by 8.
If you divide 473 by 8 you get a quotient of 59 with a remainder of so 7, 016 is evenly divisible by 8.
2. Divisibility Rules September 04, 2015
The rule of....
If the sum of the digits is divisible by 9, then the number is divisible by 9. (JUST LIKE RULE 3)
Example
2,376 2+3+7+6= 18 which is a multiple of 9so 2,376 is evenly divisible by 9