Tn = 324, Sn = 484, r = 3, a =?, n =?
Now, Sn = \(\frac{rT _n−a}{r−1}\)
∴ 484 = \(\frac{3(324)−a}{3−1}\)
∴ 484 = \(\frac{972−a}{2}\)
∴ 484 × 2 = 972 – a
∴ a = 972 – 968
a = 4
Now, Tn = a.rn-1
∴ 324 = 4(3)n-1
∴ 324 / 4 = (3)n-1
∴ (3)4 = (3)n-1
∴ 4 = n – 1 ( Base are equal, Index are also equal)
∴ n = 5