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how many times the digit 7 is written while writing the numbers from 1 to 1,00,00,000?

Sathya , 13 Years ago
Grade 10
anser 1 Answers
Aman Bansal

Last Activity: 13 Years ago

Dear Sathyaram,

 

First, change the numbers from "1 to 10,000,000" to the boundaries  to 
1) Changing the "boundaries" from   to 
2) Leading zeros wont affect the number of sevens.

As such, we have     

By symmetry, each digit appears exactly as often as each other digit. Every combo of digits gives a viable seven digit number. Thus,

 

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