Question

1. Find the sum of the geometric sequence –3, 15, –75, 375, … when there are 8 terms and select the correct answer below.

–195,312
195,312
292,968
–292,968

Answer 1

you can add the 8 terms up like it is
or you can use a formula if you wish

Answer 2

2. Finn bought a yoyo from a company that claims that, with each retraction, the string rolls up by 80% of the original length. He sets up a tape measure and throws the yoyo 3 times. His data are charted below.


Throw Length of string (feet)
1 3
2 2.4
3 1.92


Finn wants to find the sum of the length of string after 10 throws. What is the sum of the lengths, rounded to the nearest hundredth?
13.39 feet
15.00 feet
4.46 feet
0.40 foot

3. Evaluate S5 for 300 + 150 + 75 + … and select the correct answer below.

18.75
93.75
581.25
145.3125

Answer 3

\[S_n=\frac{a_1(1-r^n)}{1-r} \\ \text{ where} n=8 \text{ since you want to find the sum of the first 8 terms }\]

Answer 4

@freckles just add the terms that's it?

Answer 5

@freckles or did you mean multiply?

Answer 6

sum means to add

Answer 7

you are to find the sum not the product

Answer 8

you have to find the other 4 terms though if you do it that way

Answer 9

but I would just use the formula because it is quicker to me

Answer 10

i must go
good luck

Answer 11

@freckles thanks