The fifth term of

Nth term of GP is T_n = ar^{n - 1}

T₅ = a.r⁴

81 = a.r⁴…(1)

Nth term of GP is T_n = ar^{n - 1}

T₂ = a.r¹

24 = a.r¹…(2)

Divide 1 by 2

⇒

⇒

⇒

Substituting r in 2 we get,

a = 16

∴ The series is 16, 24, 54, …

∴ Sum of GP for n terms = …(1)

⇒ a = 16, r = , n = 8

∴ Substituting the above values in (1) we get,

⇒

⇒

⇒ 788.125