Erm...how does one work out a Mach number simply from being given a temperature and an altitude? A plane at at this altitude (and subject to this temperature) can be flying at any speed it likes...unless this "Mach number" the question talks about is a measure of the speed of sound at this altitude and temperature, as a fraction of its sea level value? I can't see any other explanation.
I'm not at the ATPL stage yet, having just finished uni, but this question sounds a bit odd...or am I not well-versed enough in ATPL phraseology!?
V1R
