InterviewSolution
Saved Bookmarks
| 1. |
Find the sum of the sequence 7, 77, 777, 7777, . . . to n terms. |
|
Answer» `S=7+77+777+7777..........n terms` `S=7(1+11+111.......n terms)` `S=7/9(9+99+999.......n terms)` `S=7/9((10-1)+(100-1)+(1000-1).......n terms)` `S=7/9(10+100+1000......n terms.-(1+1+1+1....n terms)` `S=7/9( (10((10)^n-1))/(10-1)-n)` `S=7/9( (10((10)^n-1))/(9)-n)` |
|