If a,d and Sn are first term, common difference and sum of first nth terms of se

If a,d and Sn are first term, common difference and sum of first nth terms of series, then Sb =

n/2[2a+(n-1)d]

n/2[a+(n-1)d]

n/[2a+(n-1)d]

a+(n-1)d

Answer : A

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1) If a = 3, r = 2, then nth term of G.P is

2.3n-1

2) 5th term of G.P 3,6,12,… is

15

48

2

3

3) If A, G, H are arithmetic, geometric and harmonic means between a and b respectively, then A,G,H are

in G.P

in A.P

in H.P

Real numbers

4) G1,G2,…,Gn are said to be n geometric means between a and b if a,G1,…Gn,b is

a sequence

not a sequence

G.P

A.P

5) Sum of n terms of G.P is

n/2[2a+(n-1)d]

a(1-rn)/(1-r)

2ab/(a+b)

a+b/2