Homework Help: math

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 S₂₅ = 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

Answer this Question

Related Questions

General - Please understand that I am not upset with anyone or whatever I just ...
algebra - (a minus sqrtx)^2=25 I have no idea of how to work this problem where ...
To Sam: Penn Foster answers - Please do not post any more answers. Jiskha is not...
Algebra - I was wondering if someone could check over these answers for me. Find...
to Nazgul - You have posted the same thing, time after time this morning, and ...
Asap can someone pplz check these answers - Please check my answers I have 2 do ...
social 10 COULD SOMEONE PLEASE HELP ME! - Historical Globalization & ...
Math - can you help me with the homework that I am doing right now that is math ...
math - I know youall are very busy an that answering posts takes time, but I am ...
Math HELP - I have my answers at the bottom but please do these questions so I ...

For Further Reading

First Name:
School Subject:
Answer: