Equation

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Crunch77

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Joined
Dec 3, 2012
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7
Hi

I'm very rusty at equations, and I need to isolate "S" in the following.


D = (S - K) * 100 / S

I've tried a few "routes", but always end up at a dead end. :(
 
Can you post what you have tried so we can guide you and show you why what you've tried doesn't work?
 
S = 100S/D - 100K/D -->
100K/D = 100S/D - S stuck....

Or

D/100 = (S - K) / S -->
s * D / 100 = S - K -- >
(S * D/100) + K = S stuck.....


EDIT: and thank you for taking time to answer my question. :)
 
What you have done is not wrong, it just isn't taking you in the right direction.

Let's take this one step at a time. First multiply both sides of the equation by S to clear that denominator on the right side. What do you get?
 
I recommend not switching to lowercase letters for the variables. Use the originals all the way through.

Next, distribute the 100 to the two terms within the parentheses on the right, so that we have two separate terms. What do you get?
 
s * d = 100s - 100k (changed to lowercase, since it keeps changing them by itself.)
 
Last edited:
Sorry, I didn't realize they were being switched on you.

Okay, now we have two terms that have s as a factor, so we want to get them on the same side of the equation. I recommend first adding 100k to both sides, then subtracting s*d from both sides. What to you get?
 
Good, what you have is correct. Now, both terms on the right have s as a common factor, so factor it out. What do you get?
 
Where did the p come from? Except for that, you are correct.
 
s = 100k / (100 - d)

Oops. Thank you again so much. It's been around 15 years since I had to do any sort of thing like this. :)
 
Glad to help, and welcome to the forum! :mrgreen:
 
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