Direction: Find the missing number in the following number series.
176, 216, 196, (?), 201, 203.5, 202.25
176 + 80/2 = 216
216 – 80/4 = 196
196 + 80/8 = (206)
206 – 80/16 = 201
201 + 80/32 = 203.5
203.5 – 80/64 = 202.256. If 65 : a ∷ 25 : 6, then a is equal to -