# Math Help - Value of S?

1. ## Value of S?

Could someone help with this, A hint is provided but I cannot seems to find a solution.
__________________________________________________ _______________________

$S = 1 + 0.5 + 0.25 + ... + (\frac{1}{2})^n$

What is the Value of S? [HINT = Multiply S by 2, then Solve]

2. Originally Posted by Air
Could someone help with this, A hint is provided but I cannot seems to find a solution.
__________________________________________________ _______________________

$S = 1 + 0.5 + 0.25 + ... + (\frac{1}{2})^n$

What is the Value of S? [HINT = Multiply S by 2, then Solve]
you have actually this
$S = 1 + \frac{1}{2} + \left( {\frac{1}{2}} \right)^2 + ... + \left( \frac{1}{2} \right)^n$ --------(a)

if we multiply 2, we have

$2S = 2 + 1 + \frac{1}{2} + \left( {\frac{1}{2}} \right)^2 + ... + \left( \frac{1}{2} \right)^{n-1}$ ----------(b)

subtracting (b) - (a), we have

$S = 2 - \left( \frac{1}{2} \right)^n$, so if we take n to be a large number, then $S \approx 2$

3. Originally Posted by kalagota
$S = 2 - \left( \frac{1}{2} \right)^n$, so if we take n to be a large number, then $S \approx 2$
What do you mean by n is larger number? Can you explain how the approximation of 2 is obtained?

4. Originally Posted by Air
What do you mean by n is larger number? Can you explain how the approximation of 2 is obtained?
Hello,

you are supposed to know that

$\lim_{n\to \infty}\left(\frac12\right)^n = 0$

$\lim_{n\to \infty}\left(2- \left(\frac12\right)^n \right)= 2-0 = 2$