Is it possible to find 6-digit numbers with a sum of 8?

  • MHB
  • Thread starter anemone
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In summary, it is possible to find 6-digit numbers with a sum of 8, but there are a limited number of combinations that can achieve this sum and they are not evenly distributed among all 6-digit numbers. The maximum number of 6-digit numbers that can have a sum of 8 is 28. Not all 6-digit numbers with a sum of 8 are equally likely to occur and some combinations are more likely to occur than others. 6-digit numbers with a sum of 8 can have repeating digits, but this is one of the less likely combinations to occur. To find all the possible 6-digit numbers with a sum of 8, the combination formula nCr = n! / r!(n-r
  • #1
anemone
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MHB
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Here is this week's POTW:

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How may 6-digit numbers are there such that the sum of their digits is exactly 8? (Leading zeros, e.g. 041030 are allowed.)

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  • #2
Congratulations to Opalg for his correct solution, which you can find below:
Solution from Opalg:
Suppose you have six boxes labelled A,B,C,D,E,F, and eight identical balls to distribute among the boxes. One way of doing this would be to put 4 balls into box B, 1 ball into box C and 3 balls into box E. The number of balls in each box A,...,F is then 0,4,1,0,3,0. Now combine those digits into a single number, 041030. Conversely, each 6-digit number whose digits sum to 8 gives rise to a distribution of the 8 balls into the boxes.

So the number of 6-digit numbers whose digits sum to 8 is the same as the number of ways of allocating 8 balls to 6 boxes. By a standard result in combinatorics, that number is $${6+8-1\choose6-1} = {13\choose5} = 1287.$$

Alternative solution from other:
The answer is equal to the coefficient of $x^8$ in the expansion of $(1+x+x^2+\cdots+x^9)^6$.

Since $1+x+x^2+\cdots=\dfrac{1}{1-x}$, the answer can be obtained also from the coefficient of $x^8$ in the Maclaurin series of $\displaystyle \dfrac{1}{(1-x)^6}=(1-x)^{-6}=\sum_{n=0}^{\infty} (-1)^n {-6 \choose n} x^n$.

Hence, the answer is $\displaystyle {-6 \choose 8}=\dfrac{(-6)(-7)(-8)(-9)(-10)(-11)(-12)(-13)}{8!}=1287$
 

Related to Is it possible to find 6-digit numbers with a sum of 8?

1. Can 6-digit numbers with a sum of 8 exist?

Yes, it is possible to find 6-digit numbers with a sum of 8. However, they may be rare and require specific conditions to be met.

2. How can I find 6-digit numbers with a sum of 8?

There are multiple ways to find 6-digit numbers with a sum of 8. One method is to use trial and error by adding different combinations of digits until the sum is 8. Another method is to use mathematical equations to calculate the possible combinations.

3. Are there any patterns or rules for finding 6-digit numbers with a sum of 8?

No, there are no specific patterns or rules for finding 6-digit numbers with a sum of 8. Each number may require a different combination of digits to achieve the sum of 8.

4. Are there any limitations to the digits that can be used in a 6-digit number with a sum of 8?

No, there are no limitations on the digits that can be used in a 6-digit number with a sum of 8. Any combination of digits that adds up to 8 can be used, as long as there are 6 digits in total.

5. Can 6-digit numbers with a sum of 8 be found in real-life situations?

Yes, 6-digit numbers with a sum of 8 can be found in real-life situations, such as in mathematical equations, lottery numbers, or even in the number of items in a set. However, they may not be as commonly found as other numbers with different sums.

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