OK now this one is weird...
Found on Aviation Exam, ID 26537
Given
Mach 0.80
Flight Level FL330
OAT: ISA+15
TAS is approximately (compressibility factor of 0.94):
A 265 kts
B 480 kts [this is what I get with formulas and CR-3)
C 420 kts
D 450 kts (marked correct)
Is it me or EASA?
Of course if I multiply 480 by 0.94 I get a approximately 450 kts... but it is not correct, is it?