A Strict Digital Sum

How many different positive integers exist between 1 0 6 10^{6} and 1 0 7 10^{7} the sum of whose digits is equal to 2?

6 18 7 5 8

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3 solutions

Zeeshan Ali
Mar 1, 2016

The only possible numbers that satisfy the given conditions are:

1000001 1000010 1000100 1001000 1010000 1100000 2000000 \large{1000001} \\ \large{1000010 } \\ \large{1000100 } \\ \large{1001000 } \\ \large{1010000 } \\ \large{1100000 } \\ \large{2000000 } \\

These numbers are 07 \boxed{07} in number :)

This problem isn't that hard. It can actually be a logic problem.

Seth-Riley Adams - 5 years, 1 month ago
Kay Xspre
Mar 1, 2016

The number must be greater than 1,000,000. Here, to make sum of the digits be 2, another number of 1 must be inserted in place of any single zero, which can be done in six ways, and the last way is 2,000,000, hence there are 7 methods.

The numbers are:

1000001

1000010

1000100

1001000

1010000

1100000

and

2000000

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