Correct Answer - Option 2 : x = 10, y = 20, z = 40
Concept:
nth term of the G.P. is an = arn−1
Calculation:
GIven series: 5, x, y, z, 80
We have 1st term, a = 5, and 5th term,a5 = 80
∴a5 = 5 (r)5-1
⇒ 80 = 5r4
⇒r4 = 16
⇒r = 2
∴ x = 5(2)2-1 = 10
And, y = 5(2)3-1 = 5 × 4 = 20
Also, z = 5(2)4-1 = 5 × 8 = 40
Hence, option (2) is correct.