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Math 8 presentation: Divisibility rules
Transcript of Math 8 presentation: Divisibility rules
For example: 320 is divisible by 10 because the last digit is 0, 457 on the other hand is not divisible by 10 because the last digit is 7 not 0. Divisibility rule for 9 The divisibility rule for 9 is simple. If you add all the digits up and they equal 9 or any other number that equals 9 it is divisible by 9.
For example: 27, 2+7=9 so 27 is divisible by 9.
288, 2+8+8=18 and 1+8=9 so 288 is divisible by 9. Divisibility rule for 5 The divisibility rule for 5 is almost as easy as 10. If the last digit is 5 or 0 it is divisible by 5.
For example: 22, the last digit is 2 so it is not divisible by 5
40, the last digit is 0 so it is divisible by 5 Divisibility rule for 7 The divisibility rule for 7 is definitely the hardest of all that I have shown you. To find out if a number is divisible by 7 you must double the last digit, then subtract it from the remaining digits of the number. If the answer is divisible by 7 then the original number also will be.
For example: 616, 6x2=12, 61-12=49 and 49 is divisible by 7, therefore 616 is divisible by 7 It is easy to check if a number is divisible by 10. How many other "tests of divisibility" can you find? divisibility by 5, 7 or 9? Divisibility rule for 1 The divisibility rule for 1 is simple because all
numbers are divisible by 1. Divisibility rule for 2 Any even number is divisible by
For example, 368 is divisible by
2 because 8 is and even number. Divisibility rule for 3 A number is divisible by 3 if the
sum of the digits is a number
divisible by 3.
For example, 468, 4+6+8= 18 &
18 is divisible by 3. Divisibility rule for 4 A number is divisible by 4 if the
last 2 digits are divisible by 4.
For example, 112, 12 is divisible
by 4 so 112 is divisible by 4. Divisibility rule for 6 You know a number is divisible by 6 if you
combine the rules for 2 and 3.
For example, 12 is divisible by 6 because it
passes the rules for both 2 and 3. Divisibility rule for 8 A number is divisible by 8 if the last 3
digits are divisible by 8.
For example, 9640 is divisible by 8 because
640/8=80 Divisibility rule for 11 To determine if a number is divisible by 11 you must alternately add & subtract the digits from left to right.
For example: 726 is divisible by 11 because, 7-2+6=11 Divisibility rule for 12 To see if a number is divisible by 12 it must pass the rules for both 2 and 3. Divisibility rule for 13 To check if a number is divisible by thirteen you must add 4 times the last digit to the rest.
For example: 637, 63+7x4=91, 9+1x4=13