Posted by Jon on Wednesday, December 12, 2007 at 8:53am.
Hi I need someone to check my answers I'll show whatever work I have but for time purposes I'll just post my answers because I think I have most of them correct. Thanks!
1)Find the 20th term of the arithmetic sequence in which a1=3 and d=7.
A)143
B)136
C)140
D)133
I chose B
2)Write an equation for the nth term of the arithmetic sequence 3,3,9,15...
A)aN=n+6
B)aN=6n+9
C)aN=6n9
D)aN=n3
I chose B
3)Find the two arithmetic means between 4 and 22.
A)10,16
B)8,16
C)8,12
D)13,13
I chose A
4)Simplify: Find Sn for the arithmetic series in which a1=3,d=1/2,and aN=15
A)225
B)9
C)45
D)210
I chose B
5)ok this one's tricky to type but its with sigma so here it is.
There is a sigma sign and there is an 8 on the top of it and k=3 below. In parentheses to the right is (403k) and the question is Find.
A)45
B)282
C)90
D)141
I chose D. this question is tricky but if you read it slowly and you know about sigma you'll be able to help. Thanks again.

math  Reiny, Wednesday, December 12, 2007 at 9:33am
Your #2 and 4 are not correct
#2:
you picked B which is t_{n} = 6n+9
if you let n=1 you get 15 as your first term, you should obtain 3
doesn't C give you that result?
#4:
t_{n} = 15
15 = 3 + (n1)(1/2)
12 = (n1)/2
24 = n1
n=25
So S_{25} = 25/2[6 + 24(1/2)]
= 25/2[18]
= 225 which is A

math  Jon, Wednesday, December 12, 2007 at 9:41am
ok thanks. Did you check the others?

math  Reiny, Wednesday, December 12, 2007 at 9:43am
the others were ok
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