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April 25, 2015

Homework Help: Math

Posted by Crystal on Tuesday, January 8, 2013 at 6:02pm.

I'm learning series and sequences (grade 11).

Please check that my steps show I understand what I'm doing/the concept and my answer as well:

5. The consecutive terms of an arithmetic sequences are 3.6, y, 8.2. Find the value of y.

This seems to be a sequence question but I used the formula for series.... Is there a better way to solve this question???

S3 = 3/2 (3.6+8.2)
=3/2(11.8)
=17.7

17.7 = 3/2(2 3.6 + (3-1)d)
17.7 = 3/2(7.2+2d)
17.7 = 10.8 + 3d
17.7 - 10.8 = 3d
6.9 = 3d
2.3 = d

So y = 5.9

I feel like I'm not doing this properly ... Please help! I have a quiz tomorrow on sequences ):

I also used the same method for this question:
Insert 3 evenly spaced numbers between -2 and 10. My final answer was 3 = d, so : -2, 1, 4, 7, 10.

What is the proper way to solve these questions? I don't think I'll be able to use series formulas on the quiz tomorrow which is only on sequences!

Also, I'm stuck on this question:

Find the 10th term of the arithmetic sequence where the first term is 5 and the 4th term is 17.

How would you solve this question?

Thank you so much in advance!

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