The second term in a geometric sequence is 20. The fourth term in the same sequence is 45/4, or 11.25. What is the common ratio in this sequence?

Question

Giana Sosa

Mathematics

13 February, 08:14

The second term in a geometric sequence is 20. The fourth term in the same sequence is 45/4, or 11.25. What is the common ratio in this sequence?

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Answers (1)

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Lilian Mclean · Answer 1

We use equations for geometric sequence. We do as follows:

a (n) = a (1) r^ (n-1)

20 = ar^ (2-1)

20 = ar

a = 20/r

11.25 = ar^ (4-1)

11.25 = ar^3

11.25 = (20/r) r^3

r = 0.75

Hope this answers the question. Have a nice day.