If `S_n = sum_(r=1)^n (1+2+2^2+2^3+....r terms)/2^r`, then S_n is equal to

If S_n=sum_(r=1)^n(1+2+2^2+ .......+2^r)/(2^r), then S_n is equal to (a) 2^n n-1 (b) 1-1/(2^n) (c) n -1+1/(2^n) (d) 2^n-1

if S_(n)=sum_(r=1)^(n)(1+2+2^(2)......... rterms )/(2^(r)) then S_(n) is equal to

If S_(n)=sum_(r=1)^(n)(1+2+2^(2)+......+2^(r))/(2^(r)), then S_(n) is equal to (a)2^(n)n-1( b) 1-(1)/(2^(n))(c)2n-1+(1)/(2^(n))(d)2^(n)-1

If S_(n)=sum_(r=1)^(n)(2r+1)/(r^(4)+2r^(3)+r^(2)), then S_(10) is equal to

If S_(n) = sum_(r=1)^(n) (r )/(1.3.5.7"……"(2r+1)) , then

If s_n= sum_(r=0)^n 1/(^"nC_r) and t_n=sum_(r=0)^n r/("^nC_r) then t_n/s_n is equal to