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Hi, I don't know how to solve this problem. Could someone help me?

 

How many -digit numbers are there, such that the sum of the digits is divisible by ?

 

Thanks!!!

 Mar 10, 2020
 #1
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Write your question accurately !!  How many what? 4-digit, 5-digit, 6-digit numbers? And is divisible by what number?

 Mar 10, 2020
 #2
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Sorry, I meant to write how many 10 digit numbers are there, such of the digits is divisible by 5? The digits can be repeated.

 Mar 10, 2020
 #3
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Do you want the SUM of the 10-digit number to be divisible by 5? Example:1234567890=45 which is divisible by 5.

 Mar 10, 2020
 #4
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Yes, I'm so sorry for the confusion.

 Mar 10, 2020
 #5
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This is an arithmetic sequence as follows:

 

N/2 * [2*1000000004 + 5*(N - 1)] =9900000002700000000, solve for N

 

N =1,800,000,000 - 10-digit numbers that are divisible by 5.

 Mar 10, 2020
 #6
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Thank you so much!

 Mar 12, 2020

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