Sum the series `1/(2xx5) + 1/(5xx8) + 1/(8xx11)`+….. Upto n terms.

The sum to n terms of the series (1)/(2) + (3)/(4) + (7)/(8) + (15)/(16)+…. is equal to :

Find the sum to n terms of the series given below:- 1/(1xx2)+1/(2xx3)+1/(3xx4) +....

Find the 20th term of the series 2xx4 + 4xx6 + 6xx8 +...+n terms.

If (1)/(2 xx 4) + (1)/(4 xx 6) + (1)/(6 xx 8) + …… n terms = (kn)/(n +1) then k is equal to

Study the pattern: 1 xx 8 + 1 = 9

Find the sum of the series – 1 + 5 + 11 +….to n terms.

If the sum to infinity of the series : 1-(1+d)xx1/3+(1+2d)xx1/9 -(1+3d)xx1/27+ ......... is 9/16 , find d .

Prove that the sum to n terms of the series 11 + 103 + 1005 + …. Is (10/9) (10^(n)-1)+n^(2) .