The 5th term in a geometric sequence is 120. The 7th term is 30. What are the possible values of the 6th term of the sequence?

Question

johnweldon1993 · Answer

Well if we were going the other way....we could see that

30 * 2 = 60
60 * 2 = 120

so that would be a way to approach it and see that a possible answer for the 6th term could be 60 and the common ratio would be 1/2 :)

anonymous · Answer

$$A.60 B.\pm60C.75D.\pm75$$ are my choices

whpalmer4 · Answer

You're trying to find 1 geometric mean between 120 and 30.  120:x = x:30 or
$$\frac{120}{x}= \frac{x}{30}$$$$x^2=3600$$$$x=60$$

radar · Answer

120r^2= 130
$$r ^{2}=30/120=1/4$$$$r ^{2}=1/4$$

whpalmer4 · Answer

$$120r^2=30$$ I think you mean...

radar · Answer

Take it the next step.

anonymous · Answer

So its 30 instead of 130? Im confused.

johnweldon1993 · Answer

the answer choice would be 60....but they are explaining exactly how to arrive at it :)

anonymous · Answer

Are you 100% sure?

whpalmer4 · Answer

I was just correcting a typo in @radar's first line...was hoping to avoid you getting confused about where he got 130 from, but ended up confusing you about something else instead, can't win :-)

johnweldon1993 · Answer

quite :)   ...what radar and whpalmer were doing was showing you how the common ratio would be calculated as 1/2 ...and you would have used that to solve this :)

anonymous · Answer

Its 60, not 60(+-)?

anonymous · Answer

I need to know for sure.

radar · Answer

|dw:1369969115914:dw|