Middle Term for this sequence? 8, 11, 14, ... , 74

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luv2show

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Oct 6, 2008
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Okay, I'm sorry, this is probably a very stupid question :oops:
We just started doing this in school today and the teacher wanted us to go and try and teach ourselves and she'd grade this assignment she gave to us tonight. :x

Question:

8,11,14,...,74. Is there a middle term for this sequence? Explain your answer. If so then find the middle term.

Asnwer ??

I'm thinking that there is no middle term because if you have a sequence such as 2,4,6,8 - the middle term is 5 and that is not a number in the sequence.
So the middle number for my question would be (8 + 74)/2 = 41 ...

Rough work...
tn = a+(n-1)d
41=8+(n-1)(3)
41=8+3n-3
41=5+3n
41-5 = 3n
36/3=3n/3
12 = n
What the heck does that give me?

It doesn't make sence to me... help please :?: I'll probably have some more questions to post as well.
Thanks so much!
 
Re: Middle Term for this sequence?

Your sequence is not arithmetic, since the difference between successive terms is not constant. The first three terms can be fit exactly by a quadratic, but not one that leads to a 74. So there is a problem somewhere else.
 
Re: Middle Term for this sequence?

Sorry, that 15 is supposed to be a 14. I just fixed it... sorry!
 
Re: Middle Term for this sequence?

How many terms are there in the sequence 8,11,14...74 -- 23

Surely there is a middle term!!!
 
Re: Middle Term for this sequence?

How did you get 23?
I would have gone (74+8)/2 = 41 ...
 
Re: Middle Term for this sequence?

You study the chapter carefully. You have done the work - but you do not understand your own work - because you are blindly using formulas.

I was trying to give hints about what you found.

8,11,14,17,20,23,26,29,32,35,38,41,44,47,50,53,56,59,62,65,68,71 & 74 - how many numbers are there.

There are 23 numbers - that is called number of terms in the sequence.

The middle term would be the twelfth (12) term - which is 41.

The formula that you used works for arithmetic progression - it won't work for other types of sequences.
 
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