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Subject: geometric sequence
Name: Wanda
Who is asking: Parent
Level: Middle
Question:
the fifth term of a geometric sequence is 5/16. the common ratio is 1/2. What are the first four terms of the sequence. I am a parent helping my child. thank you
Hi Wanda,
A geometric sequence has the form
a, ar, ar 2, ar 3, ar 4, ar 5, ar 6,...
where the first term is a and the common ratio is r.
If you look at the sequence above you see that the fifth term is ar 4, and hence
ar 4 = 5/16.
You also know that r = 1/2 and hence r 4 = 1/16. Thus
ar 4 = a/16 = 5/16
Thus a = 5.
Penny
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