Question

Evaluate S5 for 600 + 300 + 150 + … and select the correct answer below.

Answer 1

1,162.5
581.25
37.5<--my answer
18,600

Answer 2

@surjithayer

Answer 3

it should be greater than 1050
600+300+150+75+37.5=?

Answer 4

I suppose so? Isn't it a geometric series?

Answer 5

correct.

Answer 6

So, would I be correct?

Answer 7

hold on.

Answer 8

600{(1/2)^5-1}/(1/2-1)

Answer 9

@phi

Answer 10

116.5 Am I right?

Answer 11

You're adding up 5 numbers.
The first of which is 600.

How did they then add up to 116.5? :o
That's even smaller than the first number that you're adding...

You silly billy -_-

Answer 12

:D! Hahaha whoops! So what should I do?

Answer 13

\[\large\rm S_n=a_1\frac{1-r^n}{1-r}\]So you determined that your common ratio, \(\large\rm r\), is 1/2 since you're dividing by 2 each time.
So we'll plug in all of the information,
\[\large\rm S_5=600\cdot \frac{1-\left(\frac{1}{2}\right)^5}{1-\frac{1}{2}}\]

Answer 14

And then let mr calculator do the rest :O
understand how to punch it all in?

Answer 15

Not really, but I'll try :)

Answer 16

So, for the fraction part I got 1.9375.

Answer 17

If you want to punch it all in at once,
I would try something like this,\[\large\rm 600*((1-.5\wedge5)\div(1-.5))\]Otherwise, if you like to do it piece by piece, that's fine also :)

Answer 18

(I replaced 1/2 with .5 in my calculator so it's easier to deal with).

Answer 19

Ok:) Then, i got 1162.5 as an answer :)

Answer 20

1.9375? That sounds correct for your fractional part.
Then finally 1162.5?

Yayyy good job!

Answer 21

Yippee!!! If, I post another one will you answer it? And thanks so much btw!!!

Answer 22

I'm hungrehhh, I need to make some foods :P
but ya I'll try to come look if I get a chance.

You can use the @zepdrix and it'll get my attention better than the message box.

Answer 23

Ok, thanks so much:)