I apologize in advance if this has already been posted, but I tried searching for a similar thread and could not find. I cannot seem to the Interest Rate Party Equation from CFAI reading 18 p 565. I thought IRP was: F/S = 1+ a / 1 + b or F = S x 1+ a / 1 + b but the equation on page 565 is: F = S x 1+ b / 1 + a To me it appears as though the numerator and denominator are different for the same equation. Am I missing something with respect to Indirect versus Direct?

As far as I’m concerned, IRP is the 1st 2 equations you typed. The only time you switch numerator and denominator is to calculate anything with a “real” rate.