Solve A=P+Prt for r.

WHAT DOES THAT EVEN MEAN!?

Question

Solve A=P+Prt for r.

WHAT DOES THAT EVEN MEAN!?

jim_thompson5910 · Answer

it means "isolate r and express it in terms of A, P and t"

jim_thompson5910 · Answer

so 

r = .....

jim_thompson5910 · Answer

example (NOT the answer, just an example)

r = 2A + 4Pt

anonymous · Answer

i have no clue what that even means.

jim_thompson5910 · Answer

which part isn't making sense?

anonymous · Answer

all of it, hahaha im not trying to just get the answer, but i really have no clue what to do.

jim_thompson5910 · Answer

how good are you at solving equations?

anonymous · Answer

pretty decent.

jim_thompson5910 · Answer

we want to isolate r (ie get it all by itself)

jim_thompson5910 · Answer

how do we do this?

anonymous · Answer

r=...

jim_thompson5910 · Answer

that's what the final result will look like

jim_thompson5910 · Answer

so that's what we're aiming for

jim_thompson5910 · Answer

any ideas on how to get started getting there?

anonymous · Answer

well we have to get rid of P and t then?

jim_thompson5910 · Answer

yes so to speak

anonymous · Answer

idk how.

jim_thompson5910 · Answer

A=P+Prt

A - P=P+Prt - P ... Subtract P from both sides.

Notice how P - P = 0P = 0 which goes away on the right side

A - P = Prt

with me so far?

anonymous · Answer

yea i think so.... so you are trying to move them over to the other side?

jim_thompson5910 · Answer

exactly

jim_thompson5910 · Answer

and I'm moving them using the rules of algebra

anonymous · Answer

okay so what next? the t?

jim_thompson5910 · Answer

yes or we can move both P and t at the same time

jim_thompson5910 · Answer

A - P = Prt

A - P = r*(Pt) ... Rearrange terms

now divide both sides by Pt to completely isolate and solve for r

$$\Large \frac{A - P}{Pt} = r $$

and flip to get the final result

$$\Large r = \frac{A - P}{Pt}$$

jim_thompson5910 · Answer

So the complete step by step picture looks like this

$$\Large A=P+Prt $$

$$\Large A - P=P+Prt - P$$

$$\Large A - P = Prt $$

$$\Large A - P = r*Pt $$

$$\Large \frac{A - P}{Pt} = \frac{r*\cancel{Pt}}{\cancel{Pt}} $$

$$\Large \frac{A - P}{Pt} = r $$

$$\Large r = \frac{A - P}{Pt}$$

anonymous · Answer

so you just separated the p and t from the r that way you could move it to the other side? OHHH thanks soo much!

jim_thompson5910 · Answer

exactly, that step isn't necessary if you can see and know what's going on (so you can skip it and directly divide)