Ah, good old 1.32 (or, to be precise, 1.316074)!
When I went through CFS, the grounskool bod couldn't explain it and just said " 'cos it is!".
So I did a bit of basic mechanics and calculus:
Total drag = Zero Lift Drag + Lift Dependent Drag
i.e. D = AV**2 + BV**-2
To find the minimum drag speed, differentiate with respect to V and equate to zero:
dD/dV = 2AV – 2BV**-3 = 0
Hence VMD =(B/A)**-4
Power is the ‘rate of doing work’, i.e. Work/time or (Force x dist)/time
Hence Power = Force (in this case Drag) x velocity
P = DV
Thus P = AV**3 + BV**-1
Again, to find the minimum power speed, differentiate with respect to V and equate to zero:
dP/dV = 3AV**2 - BV**-2 = 0
Hence VMP = (B/3A)**-4
The relation between VMD and VMP is thusVMD = VMP x 3**-4
and therefore VMD = 1.32 VMP
Sorry if this isn't easy to read - this basic forum doesn't support subscript or superscript notation, hence I've had to use ** as 'to the power of', so **-4 means 'the fourth root of'.
A similar argument will give you the 0.76 answer - it's the reciprocal of the fourth root of 3, i.e. 0.7598357.