Posted by **Jon** on Wednesday, December 12, 2007 at 7:12pm.

1)Find a1 in a geometric series for which Sn=300,r=-3,and n=4

A)15

B)15/2

C)-15

D)1/15

I chose A

2)Find the sum of the infinite geometric series. Sigma sign with infinity symbol above and n=1 below. To the right 20(-1/4)n-1

A)25

B)80/3

C16

D)does not exist

I chose A

3)Find the sum of the infinite geometric series:4+3+9/4+:...

A)16/7

B)16

C)-12

D)does not exist

I chose B

4)Write 0.72 repeating as a fraction.

A)7/9

B)8/11

C)18/25

D)7 and 2/9

I chose B but my book confuses me on how to work it out. I just divided 8 and 11 and I got .72 repeating

5)Find the fifth term of the sequence in which a1=-3,and aN+1=3aN-n

A)-301

B)-99

C)-193

D)-341

I don't know

- math(need 2nd opinion) -
**Ms. Sue**, Wednesday, December 12, 2007 at 7:20pm
Please note Damon's last post.

math - Jon, Wednesday, December 12, 2007 at 5:43pm

thanks for the help. are you possitive they are correct?

math - Damon, Wednesday, December 12, 2007 at 5:48pm

Oh good heavens, always check anything I do!

- math(need 2nd opinion) -
**drwls**, Wednesday, December 12, 2007 at 8:17pm
3. 4+3+9/4+:... = 4(1 + (3/4) + (3/4)^2^3 + ...]

= 4*[1/(1-3/4)] = 16

4. There is nothing wrong with trying the multiple choices and seeing which one works. That is what you did. There is a direct way also.

Let X = 0.727272...

0.727272...-(0.01)X = 0.727272..-0.0072727..)

= 0.720000...

Therefore

X - 0.01X = 0.72

0.99 X = 0.72

X = 72/99 = 8/11

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