4th term of a G. P is 8 and 10th term is 27. Then its 6th term is?

  1. 12
  2. 14
  3. 16
  4. 18

Answer (Detailed Solution Below)

Option 1 : 12
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Detailed Solution

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Concept:

Let us consider sequence a1, a2, a3 …. an is a G.P.

  • Common ratio = r = 
  • nth  term of the G.P. is an = arn−1
  • Sum of n terms = s = ; where r >1
  • Sum of n terms = s = ; where r <1

Calculation:

Given:

4th term of a G. P is 8 and 10th term is 27

nth  term of the G.P. is Tn = a rn-1

∴ T4 = a. r3 = 8      ----(1)

T10 = a r9 = 27      ----(2)

Equation (2) ÷ (1), we get 

∴ 

T6 = a r5

= a r3.r2

= 12

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