Math New Drill : Level 2 (SNJ00-0705-L2) Integers not including 7

In integers from 1 to 3000, find the number of figures that do not use number 7.








Answer
2187 pieces

Solution
There are eight in 1~9. 

There are 8×9 = 72 in 10~99. 

There are 8×9×9 = 648 in 100~999. 

There are 1×9×9×9 = 729 in 1000~1999. 

There are 729 in 2000-2999, too. 

There is one which is 3000. 

There are 8 + 72 + 648 + 729×2 = 2,187 in total.