# Thread: A+B=C Solve for A when B is % based on A

1. ## A+B=C Solve for A when B is % based on A

I feel like this is so simple but I just can't seem to pull it out of the aging brain......

I have a Product Cost represented as A
I have a Fee for the product that is a percentage of the Product Cost as B B=(A*.10)
This gives me the Total Cost of the product as C

Now if I know the Product Cost is 500.00 A=500
If the Fee is 10% of the Product Cost then 500*.10=50 B=50 (the Percentage is not always constant and can change but it is always based on the product cost of A)
A+B=C
500+50=550 C=550

However, if I don't know the Product Cost but am only given the Total Cost and the Fee, How can I find out what the Product Cost is?
C=A+B
or
C=A+(A*.10)
How do I solve for A?

2. ## Re: A+B=C Solve for A when B is % based on A

$A + B = C$

$A + pA= C,~\text{where$p$is the percentage used to obtain$B$}$

$(1+p)A = C$

$A = \dfrac{C}{1+p}$

3. ## Re: A+B=C Solve for A when B is % based on A

I know this probably seems very simplistic but it is a very deep part of a more complicated excel formula and I'm afraid I could see the Trees for the Forest.
Excel got in the way!!
I couldn't see the math for the excel!!

thanks so much!!

4. ## Re: A+B=C Solve for A when B is % based on A

Originally Posted by lisach
I know this probably seems very simplistic but it is a very deep part of a more complicated excel formula and I'm afraid I could see the Trees for the Forest.
Excel got in the way!!
I couldn't see the math for the excel!!

thanks so much!!
I've been in those excel forests before... good luck!