Excel Formula is not working correctly

Question

I am trying to create min value for product in excel. I am using following formula which is working fine but the reverse of it does not work fine.

Min Value formula = A1+50/(500/A1)

Reverse formula which is not working fine = B1-50/(500/B1)

Original Value  Min Value   Reverse value
50              55          49.5 [ it should come 50]
120             132         118.8 [it should come 120]
220             242         217.8
4               4.4         3.96
16              17.6        15.84

Please let me know where I am wrong.

Answer 1

Simplify the formula to factor out A1 so it can be reversed

A1 + 50/(500/A1) 
=> A1 + A1 * 50/500
=> A1 * (1 + 50/500)
=> A1 * 1.1

Reverse is = B1 / 1.1