InterviewSolution
Saved Bookmarks
| 1. |
Find the sum upto n terms of the series `0.b+0.b b+0.b b b +0.b b b b+"......",AA " b" in N " and "1 le b le 9.` |
|
Answer» Let `S=0.b+0.b b+0.b b b +0.b b b b+"......""upto n terms"` `=b(0.1+0.11+0.111 +0.1111+"......""upto n terms")` `=(b)/(9)(0.9+0.99+0.999+0.9999+"......""upto n terms")` `=(b)/(9){(1-0.1)+(1-0.01)+(1-0.001)+(1-0.0001)+"......""upto n terms")}` `=(b)/(9){(1+1+1+1)+"......""upto n terms")-(0.1+0.01+0.001+0.0001+"......""upto n terms")}` `=(b)/(9){n-((1)/(10)+(1)/(10^(2))+(1)/(10^(3))+(1)/(10^(4))+"......""upto n terms")}` `=(b)/(9){n-(((1)/(10)(1-((1)/(10))^(n)))/(1-(1)/(10))}=(b)/(9){n-(1)/(9)[1-((1)/(10))^(n)]}` |
|