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# Isolating quantities — Basic example

Watch Sal work through a basic Isolating quantities problem.

## Want to join the conversation?

• I moved pgh to the left instead and solved from there and I got a different answer. Is my answer totally wrong ?
• easyy peasy
• why isnt the answer c?
• In this question we're given an equation and asked to solve for something other than the variable that it's normally solved for. We just do our algebra in order to get the result that we want.
P = P_0 + pgh
pgh = P - P_0
h = (P - P_0) / pg

The answer isn't C here because we have to first isolate the pgh term before dividing by pg. Whenever multiplying/dividing, we have to do it to every single term, and C) assumes we did order of operations wrong.
• At , Sal mentions the Greek letter rho. What does rho mean?
• Rho is just a letter, so it doesn't have any special meaning. In science, you may come across it used to talk about densities.
• why is it so complex and complicated
• because the ancient math guys wanted to make us suffer
• So, we basically try to cancel out both sides of the equations that are equal, and then we isolate the necessary variable, and finally we simplify down to get our answer.
• i didnt think i was going to get it but i get it now
• In practice it was p= l+h*2, you first divide 2 to both sides and it becomes p divided 2, and then minus l separately but here you write p-po over pg combined?
• What is sub zero... is it like a variable or an equation?
• Well, `sub zero` is an example of keeping different quantities that have the same variable separate using a subscript. In this case we have two kinds of pressure: