Recent questions tagged number-series

10 votes
3 answers
31
8 votes
5 answers
33
Find the sum to $'n'$ terms of the series $10+84+734+\dots$$\frac{9(9^n+1)}{10} +1$$\frac{9(9^n-1)}{8} +1$$\frac{9(9^n-1)}{8} +n$$\frac{9(9^n-1)}{8} +n^2$
2 votes
3 answers
39
The series $$\sum ^{\infty }_{n=1}\frac{(-1)^{n+1}}{\sqrt{n}}$$ Converges but not absolutely. Converges absolutely. Diverges. None of the above.
2 votes
2 answers
40
The sum of the series $$\frac{1}{1 \cdot 2}+ \frac{1}{2 \cdot 3}+ \frac{1}{3 \cdot 4} + \dots +\frac{1}{100 \cdot 101}$$$\frac{99}{101}$$\frac{98}{101}$$\frac{99}{100}$No...
1 votes
1 answer
41
I'm having hard time understanding how following series converges ; 1 + 2/5 + 3/5^2 + 4/5^3 + 5/5^4 + ............ infinity
12 votes
3 answers
42
24 votes
2 answers
43
24 votes
1 answer
44
Find the sum of the expression$\frac{1}{\sqrt{1}+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+\frac{1}{\sqrt{3}+\sqrt{4}}+............+\frac{1}{\sqrt{80}+\sqrt{81}}$$7$$8$$9$$10...