Question

The sum of 0.2 + 0.004 + 0.00006 + 0.0000008 + . . . . . to $$\infty $$ is

A. $$\frac{{200}}{{891}}$$
B. $$\frac{{2000}}{{9801}}$$  
C. $$\frac{{1000}}{{9801}}$$
D. None of these
Answer :   $$\frac{{2000}}{{9801}}$$
Solution :
Sum $$ = \frac{2}{{10}} + \frac{4}{{{{10}^3}}} + \frac{6}{{{{10}^5}}} + \frac{8}{{{{10}^7}}} + .....\,{\text{to }}\infty $$        which is an arithmetico-geometric series

Releted MCQ Question on
Algebra >> Sequences and Series

Releted Question 1

If $$x, y$$ and $$z$$ are $${p^{{\text{th}}}},{q^{{\text{th}}}}\,{\text{and }}{r^{{\text{th}}}}$$   terms respectively of an A.P. and also of a G.P., then $${x^{y - z}}{y^{z - x}}{z^{x - y}}$$   is equal to:

A. $$xyz$$
B. 0
C. 1
D. None of these
Releted Question 2

The third term of a geometric progression is 4. The product of the first five terms is

A. $${4^3}$$
B. $${4^5}$$
C. $${4^4}$$
D. none of these
Releted Question 3

The rational number, which equals the number $$2.\overline {357} $$   with recurring decimal is

A. $$\frac{{2355}}{{1001}}$$
B. $$\frac{{2379}}{{997}}$$
C. $$\frac{{2355}}{{999}}$$
D. none of these
Releted Question 4

If $$a, b, c$$  are in G.P., then the equations $$a{x^2} + 2bx + c = 0$$     and $$d{x^2} + 2ex + f = 0$$     have a common root if $$\frac{d}{a},\frac{e}{b},\frac{f}{c}$$   are in-

A. A.P.
B. G.P.
C. H.P.
D. none of these

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