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## Try the problem

This problem of Bijection Principle is from B.Stat, B.Math Entrance.

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

## Watch the first hint

## Other useful links:-

- https://www.cheenta.com/divisibility-b-stat-hons-admission-test-2005-objective-problem-3/
- https://www.youtube.com/watch?v=8tvcymMGKMI&list=PLTDTcDkWcXuxeaAMvWpx4vGIul38dKOQp&index=5

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