check my answer?
Find S_11 for 1 + 2 + 4 + 8 + ...
I got 2047, is that correct?

Question

check my answer?
Find S_11 for 1 + 2 + 4 + 8 + ...
I got 2047, is that correct?

anonymous · Answer

wht is "S"?

anonymous · Answer

I believe that it means the sum of the series

anonymous · Answer

idk the answer to this

sloppycanada · Answer

Write out your equation for me.

anonymous · Answer

well I know that r=2 and so I multiplied by 2 for each and got 1,2,4,8,16,32,64,128,256,512,1024 and then I looked it up because I wasn't sure what to do next and they got 2047 and I wanted to know how they got that

sloppycanada · Answer

There is an equation. First you have to find the t11. T11 = term 11.

anonymous · Answer

The eleventh term is 1024 I believe

anonymous · Answer

its geometric progression, a, ar, ar^2, ar^3....
the common ratio here is 2, that is, every next term is "previous term multiplied by 2"

sum in a GP is given by the formula $$ \frac{ a (1-r ^{n})}{ 1-r }$$

anonymous · Answer

take a as 1, r as 2 and n as 11

anonymous · Answer

(1(1-2^11))/1-2

=1-2048/1-2

=2047

sloppycanada · Answer

So yes, your answer is 2047

anonymous · Answer

okay thank you