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=6n-9

D)aN=n-3

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 (40-3k) 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 + (n-1)(1/2)

12 = (n-1)/2

24 = n-1

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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