p(h) = p0*e^(-h/7991m) hPa.
also p(h) = 1013*e^(-h/7991m) hPa.
==> p(2918m) = 1013*e^(-2918m/7991m) hPa
= 1013*e^(-0,36516) hPa =703 hPa
und p(2100m) = 1013*e^(-2100m/7991m) hPa
= 1013*e^(-0,2628) hPa =779 hPa
also hat er sich um 76 hPa erniedrigt.
0,5p0 = p0*e^(-h/7991m)
==> 0,5 = e^(-h/7991m)
ln(0,5) = -h/7991m
-0,6931 = -h/7991m
-5539=-h also h=5539.
In 5539m Höhe hast du nur noch den halben Luftdruck.