where ${}_0$ is the sea$-$level density and $h$ is the altitude measured above sea level.

This equation is only an approximation for the density variation with altitude

throughout the whole atmosphere, but its simple form makes it useful for

approximate analyses. Using this equation, calculate the density at an altitude of

$45$ km $.$ Compare your result with the actual value of density from the standard

altitude tables. In the preceding equation, assume that $T=240K($a reasonable

representation for the value of the temperature between sea level and $45$ km $,$

which you can see by scanning down the standard atmosphere table$).$