Question

[Pham Trong Bach]

Tổng $S=9+99+999+\dots +\underset{2018 chu so 9}{\underset{⏟}{999...9}}$ bằng:

A.  $\frac{{10}^{2018}-1}{9}$

B.  $\frac{{10}^{2019}-1}{9}$

C.  $\frac{{10}^{2018}-18163}{9}$

D.  $\frac{{10}^{2019}-18172}{9}$

Answer 1

[Cao Minh Tâm]

Chọn D