Saved Bookmarks
| 1. |
If `(10)^9+""2(11)^1(10)^8+""3(11)^2(10)^7+""ddot""+""10(11)^9=k(10)^9`, then k is equal to(1) `(121)/(10)`(2) `(441)/(100)`(3) 100(4) 110 |
|
Answer» `(10)^9[1 + 2(11/10)^1 + 3 (11/10)^2 + ....+ (11/10)^9]` `k = 1 + 2*11/10 + 3*(11/10)^2 + ... + 100(11/10)^9` also,`11/10k = 11/10 + 2(11/10)^2 + .......... + 9(11/10)^9 + 10 (11/10)^2 ` subtracting eqn`(1)-(2):` `-k/10 = 1 + 11/10 + (11/10)^2 + ...... + (11/10))^9 - 10(11/10)^10` `S_n = (a(1-r^n))/(1-r)` `= 1 xx((11/10)^10 -1)/(11/10 - 1)` `-k/10 = 10 [(11/10)^10 - 1] - 10(11/10)^10` `= 10 xx(11/10)^10 - 10 -10(11/10)^10` `-k/10 = -10` `k=100` option 3 is correct |
|