Solving a formula for a variable?

Question

A= P(1+rt) How to solve for r ?



1/R= 1/R(subscript 1) + 1/R(subscript 2) How to solve for r?



please show steps, I'm having a difficulty with these two

Answer 1

1) A = P*(1 + rt)

=> divide by P

A / P = 1 + rt

=> subtract 1

A / P - 1 = rt

=> divide by t

(A / P - 1) / t = r

2) 1/R = 1/R1 + 1/R2

=> combine fractions on right hand side

1/R = (R2 + R1) / (R1*R2)

=> invert both sides (you can take reciprocals of both sides)

R = (R1*R2) / (R1 + R2)

Answer 2

(1) Solve the equation for (1+rt). That will give you
something = 1+rt
(2) Solve for rt. That will give you
something = rt
(3) Solve for t. That will give you
something = t

You have to quit freaking out when faced with a polynomial. Just think of it as some single variable. It obeys all the same rules any variable does, such as the, commutative and associative properties for addition and multiplication, and distributive property of multiplication over addition.

Answer 3

For question 1:

You start with distributing the P so you'll have this:
A=P+Prt

Then you subtract the P to the side with the A:
A-P=Prt

Then finally you divide both sides by Pt giving you:

(A-P)/Pt=r and that's your answer.

For the second question I'm assuming you mean solve for the R with no subscript. If so here are the steps:

multiply everything by R giving you:

1=R(1/R1+1/R2)

Then divide both sides by (1/R1+1/R2) giving you:

1/(1/R1+1/R2)=R

And i'm not sure if they want you to simplify further but if you find a common denominator on the bottom, and flip it (because there's a fraction on the bottom you can flip it and bring it to the top) that will give you:

R= (R1*R2)/(R1+R2)

Answer 4

A=P(1+rt)
A/P=1+rt
(A/P)-1=rt
((A/P)-1)/t =r

1/R= 1/R1 +1/R2
R = (1/R1+1/R2)^-1 (This is 1 over everything on the right)
Also can be written as (R1*R2)/(R1+R2) {product over sums}

Answer 5

the guy on top and bottom is wrong for the first question
no offense the part A=P(1+rt) its P times 1 not addition(P+1)
i dont get the second one but the first one is
A=P(1+rt)
A=P+Prt
A=2Prt
divide by 2P
A/2P=rt
divide t
A/Pt=r
WALA

Answer 6

A= P(1+rt)
A/P = 1+rt
((A/P)-1) = rt
r = ((A/P)-1)/t

1/R = 1/R1 + 1/R2
1/R = R2/(R1*R2) + R1/(R1*R2)
1/R = (R1+R2)/(R1*R2)
R=(R1*R2)/(R1 + R2)

There was a reason that you were supposed to learn all that Algebra ☺

HTH

Doug