Re: How many natural numbers less than 10^8 are there, whose sum of digits equals 7?

Posted by Bankelal on Dec 03, 2013; 1:31am
URL: http://discussion-forum.276.s1.nabble.com/How-many-natural-numbers-less-than-10-8-are-there-whose-sum-of-digits-equals-7-tp7584287p7584289.html

Hi XIPP,

The total no. of ways of dividing n identical items among r persons, such that each one can receive 0,1,2 or more items is (n+r-1)C(r-1).

x7+x6+x5+x4+x3+x2+x1+x0=7

Here n=7,r=8

thus ans is 14C7.

Not sure about the other question, may be from IGDIR perspective, but still I think other guys here can guide better. 

On Mon, Dec 2, 2013 at 12:46 PM, XIPP [via Discussion forum] <[hidden email]> wrote:

How many natural numbers less than 10^8 are there, whose sum of digits equals 7?

How to compute?


Also, will such question be asked in DSE/ISI entrances for Masters in econ?

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