Ah right. But in other scenarios when we just want to calculate a plain old ISA Dev, should we take pressure into account? I have never seen that done.
Incidentally, using 1.98°/1000' for the lapse, 27'/ hPa for the ISA Dev, (as suggested by Skybrary), and 120'/°C for the density; I get a DH of 5,120'. I get 5,197' if I assume 125'/°C for the density.
I agree with the OP, it is odd not to have the exact answer as an option on the multiple choice. Perhaps they took humidity into account as well. They should have stated somewhere what all the assumed factors were.
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Last edited by Uplinker; 12th Nov 2020 at 10:43.