Question

A Trickier One:

Find the Sum of Series to n terms:

\[\large \color{green}{8 + 88 + 888 + 8888 + 88888........................ }\]

Answer 1

SUM(10n-2n) = 10 x SUM(n) - 2 x SUM(n)

Answer 2

SUM(n) = n(n+1)/2

Answer 3

8/9 (10/9 (10^n -1) - n ))

Answer 4

Well Done @zscdragon

show your steps to all watching this question..

Answer 5

The expression can be rewritten as 8*(1+11+111+...)

Now divide 8 by 9, and multiply numbers in parenthesis by 9 to get:
8/9 * (9+99+999+...)

Which can be rewritten again as:
8/9 * (10+100+1000+... - (1+1+1...))

Therefore the expression is:　8/9 * (10/9 (10n -1) - n ))

Answer 6

Level 99 is now devoid of worth.

Answer 7

What??

Answer 8

What do you mean??