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add all digits in a number together over and over until you can't anymore and if that's divisible by three the whole number is divisible by three.
eg: is 324 divisible by three? let's find out. 3+2+4=? 3
2
+4
___
9
and since 9 is divisible by three so is 324.
same rule applies with 9.
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What is the converse of the sentence A number divisible by 9 is also divisible by 3?
If a number is not divisible by 3 then it is not divisible by 9.
How do you know if a number is divisible by 2 and 3?
If a number is even, it's divisible by two. If the digits of a number add up to a multiple of 3, it's a multiple of 3. For example, 342 is divisible by 3 because 3 + 4 + 2 = 9 and 9 is divisible by 3.
Is 32643 divisible by both 3 and 9?
To check for divisibility by 9 sum the digits of the number and if this sum is divisible by 9 then so is the original number. For 32643: 3 + 2 + 6 + 4 + 3 = 18 which is divisible by 9 so 32643 is divisible by 9. As 9 = 3 × 3, any number divisible by 9 is also divisible by 3, thus as 32643 is divisible by 9 it is also divisible by 3. However, for completeness: to check for divisibility by 3 sum the digits of the number and if this sum is divisible by 3 then so is the original number. For 32643: 3 + 2 + 6 + 4 + 3 = 18 which is divisible by 3 so 32643 is divisible by 3.
What is a number in between 500 and 1000 that is divisible of 3 and 9?
There are many numbers between 500 and 1000 divisible by 3 and 9. Any number divisible by 9 is divisible by 3. How about 900?
What largest 3 - digit number divisible by both 6 and 9?
999 is divisible by 9, but not by six; the next lower number divisible by 9 is 990, which is also divisible by 6, so that's the answer. Some shortcuts for divisibility: 0 is divisible by any number. If the last digit of a number is divisible by 2, the number itself is divisible by 2. If the sum of the digits of a number is divisible by 3, the number itself is divisible by 3. If the last TWO digits of a number are divisible by 4, the number itself is divisible by 4. If the last digit of a number is divisible by 5, the number itself is divisible by 5. If a number is divisible by both 2 and 3, it is divisible by 6. If the last THREE digits of a number are divisible by 8, the number itself is divisible by 8. If the sum of the digits of a number is divisible by 9, the number itself is divisible by 9. 990: 9+9+0=18, which is divisible by 9, so 990 is divisible by 9. 18 is also divisible by 3, so 990 is divisible by 3, and since 990 ends in 0 it's also divisible by 2, meaning that it's divisible by 6 as well.
