# Reverse Square Root...

This is a discussion on Reverse Square Root... within the Excel Questions forums, part of the Question Forums category; Ok I am lamost bald on trying to figure this one out. I have a formula that uses the sqaure ...

1. ## Reverse Square Root...

Ok I am lamost bald on trying to figure this one out. I have a formula that uses the sqaure root to come up with a number. Here is the formula...

Sqrt(7)*0.845+8.96 the result is 11.20. Now what I need to do is take the answer and back track to the 0.845. Basically I need to be able to use any number like 11.20 and have it come up with the rate. Make sense?

Another way to say it. The base is 8.96 in seven years they get to a mid point of 11.20. So:

sqrt([Years])*([Rate])+[Base]=Midpoint

Years = 7
Rate = 0.845
Base = 8.96
Midpoint = 11.20

When you use the function the rate changes based on the midpoint and base numbers. The base is always 20% less than mid.

I hope this makes sense and someone can help.

2. ## Re: Reverse Square Root...

To get the rate

=(Midpoint-Base)/SQRT(Years)

or given that Base is always 20% of Midpoint you can simplify to

=Midpoint/5/SQRT(Years)

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