Best Answer

81 : 8 + 1 = 9, and 9 x 9 = 81.

Here's how to figure: If the 2-digit number is ab,. then the number is equal to 10*a + b. And nine time the sum equals 9*(a + b). Set these two equal and you have:

- 9*a + 9*b = 10*a + b --> 8*b = a.

Knowing that the digits must be in the range 1 through 9: 1 x 8 = 8, and 2 x 8 = 16, so the only possibility is a=8 and b=1.

Q: What is two digit number which is nine times the sum of its digits?

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Find a four digit number whose digits will be reversed when multiplied by nine?

The answer to this question is at my website aim feliciano980

To be a 3 digit palindromic number, it must be of the form aba.I assume that a 3 digit number must be at least 100 (so that 020 for example does not count as a 3 digit number):a can be any of the nine digits 1-9;for each of these b can be any of the ten digits 0-9Thus there are 9 x 10 = 90 three digit palindromic numbers.

Nine hundred thirty (930) is the highest three digit number whose digits have a sum of 12. 9+3+0=12. Any numbers higher than that will give you an sum greater than 12.

If the sum of the digits of a given number equals nine or a multiple of nine, nine is a factor of that number.

Related questions

-8

987654321 is the highest nine-digit number with no repeated digits.

Find a four digit number whose digits will be reversed when multiplied by nine?

1 digit number: only 1 number 2 digits number: 18 numbers 3 digits number: 76 So there are 95 numbers containing 9.

987652431

The correct answer is 102,345,678. The number 012,345,678 is considered an eight-digit number; any other rearrangement of the digits, or inserting a 9 in any position, gives a larger number.

The answer to this question is at my website aim feliciano980

There are many possible solutions. One such is 132486970

The first digit can be any one of the nine digits. For each of those . . .The second digit can be any one of four digits . . . 2, 4, 6, or 8 .Total number of possibilities = (9 x 4) = 36

948,765,321

The number of strings of four decimal digits that have exactly three digits which are nine is the number of ways to choose three places to choose the nines multiplied by the number of possibilities for the other digits (because you can put all of the possibilities in an array so that each column has a different way of arranging the nines and that each row has a different set of other digits (because they do not affect each other)). The number of ways to choose the three places to choose the nines is the same as the number of ways of choosing 4-3=1 spot for there not to be a nine. The number of ways of choosing 1 spot where there are 4 spots is 4 (the first, the second, the third, or the fourth). Since there are 9 digits that are not nine, the number of choices for the other digits is 9 (since there is only one digit). Thus, there are 4*9=36 strings of four decimal digits that have exactly three digits which are nine.

Any number whose digits do not add up to 9, 18 or 27. There are 800 of them!