Question

Determine the 11th term of the series 1.5,3,6,12,…

Answer 1

Given sequence 1.5,3,6,12,...

a2/a1 = 3/1.5 = 2 ---(1)

a3/a2 = 6/3 = 2---(2)

(1) = (2) [ common ratio ]

Therefore,

Given sequence is in G.P.

first term (a) = 1.5

common Ratio (r) = 2

nth term (an) = ar^n-1

Here, n = 11

=> a11 = (1.5)×2^11-1

= 1.5× 2^10

= 1.5 × 1024

= (3/2) × 1024

= 3 × 512

= 1536

Therefore,

11 th term = 1536

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