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How can you tell if a number is divisible by 9?
Any number which is divisible by 9 contains digits which, when added together, are equal to 9 or a multiple of 9. For example, 63 is divisible by 9 because 6 + 3 = 9. 288 is divisible by 9 because 2 + 8 + 8 = 18 and 18/9 = 2.
What is the smallest number divisible by 8 and 9?
72
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.
Is 98 divisible by 9?
No. To check for divisibility by 9 add the digits together and if this sum is divisible by 9 then so is the original number. This can be repeated until a single digit remains which must be 9 for the original number to be divisible by 9. For 98: 9 + 8 = 17 → 1 + 7 = 8 which is not 9, so 98 is not divisible by 9.
How do you test if a number is divisible by 8?
Because 8 is 2 cubed, you can test if a number is divisible by 8 by dividing it by 2 three times. If the number you reach is an integer, then the number is divisible by 8. For example, 72/2 = 36/2 = 18/2 = 9. Therefore, 72 is divisible by 8. For very large numbers, if the last three digits are divisible by 8, the number itself is divisible by 8.
