![]() So 4 plus 8 is equal to 12, andġ2 clearly is divisible by 3. So this is equal to 48- in case you're not sure whether Plus 5 is 32, plus 8 is 40, plus 8 is 48. Plus 9 plus 5 plus 8 plus 8, what's this going You're divisible by 3, you really just have toĪdd up all the digits and figure out if the Number, this 5, so this is not divisible by 2. And over here, you do not haveĪ number that is divisible by 2. And right over here,Ĩ is divisible by 2, so this thing is goingīe divisible by 2. Look at the ones place and see if the ones These are divisible by 2, you really just have to Of how do you actually test to see if this isĭivisible by 2 or 5 or 9 or 10. ![]() Other videos- but really just to give you a sense ![]() Lot on the why of why they're divisible- we'll do that in ![]() If these three random numbers are divisible by any To do in this video are some real quick tests to see The number is 12, so the number 13165648 is not divisible by 11. The number is 0, so the number 2547039 is divisible by 11. (Sum of digits at odd places) - (Sum of digits at even places) It is very simple, check the number, if the difference of the sum of digits at odd places and the sum of its digits at even places, is either 0 or divisible by 11, then clearly the number is divisible by 11.įirst find the difference between sum of its digits at odd and even places. How to check a number is divisible by 11? Since 24 is not divisible by 7, neither is 2799588. Since 10 equals 5*2 (neither of which are 7), it should not influence the result. This works because, in essence, you are dividing by 10. How can I continue?įor this special case, you can just drop the zero from 27990 to 2799 and continue from there. What about the number used in this video? I tried to test the divisibility by 7 of 2799588, but at a certain point I have 27994 - (2*2) = 27990. This edit was made in response to a.ortalda's great question about divisibility by 7. If I wasn't clear with my explanation or if you need any more help, just ask. Since 75 is not divisible by 7, neither is 813 or 8256. 813 is slightly too large to tell whether it is divisible by 7 so we must repeat the process. Since 28 is divisible by 7, we can now say for certain that 364 is also divisible by 7.Įxample 2: Is the number 8256 divisible by 7?Īnswer 2: No, Double 6 to get 12. (You may have to repeat this a couple of times if the divisibility of the resulting number is not immediately obvious).Įxample 1: Is the number 364 divisible by 7?Īnswer 1: Yes: Double the 4 to get 8. If this new number is either 0 or if it’s a number that’s divisible by 7, then then original number is divisible by seven. Then, subtract this number from the rest of the remaining digits. In order to test this, you must take the last digit of the number you’re testing and double it. This one is a little weird but it really is quite simple after you practice it a couple of times. If they are, then the entire number is divisible by 8 too.Įxample 1: Is the number 8347475537272 divisible by 8?Īnswer 1: Yes, because the last 3 digits, 272, are divisible by 8.Įxample 2: Is the number 314159265358979323846 divisible by 8?Īnswer 2: No, because the last 3 digits, 846, are not divisible by 8. In order to test this, you only must check to see whether the last three digits of the number are divisible by 8. Actually, divisibility by 7 & 8 is quite easy once you get the hang of it.įirst, I will talk about divisibility by 8, since it is easier.
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