Q: 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?

A: 2nd term = ar = 20 (a = first term, r = common ratio) ... ... ... (1)
4th term = ar^3 = 45/4 .... ..... [ (2)
Divide relation (2) by relation (1)
ar^3/ar = 45/4 / 20 = 45 / (4 x 20)
r^2 = 9/16
Common ratio r = +_ sqrt(9/16) = +_ 3/4 source: yahoo ]

Expert answered|sharpies|Points 5112|

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