# A commercial jet and a private airplane fly from Denver to Phoenix. It takes the commercial jet 1.1 hours for the flight, and it takes the private airplane 1.8 hours. The speed of the commercial jet is 210 miles per hour faster than the speed of the private airplane. Find the speed of both airplanes.

A commercial jet and a private airplane fly from Denver to Phoenix. It takes the commercial jet 1.1 hours for the flight, and it takes the private airplane 1.8 hours. The speed of the commercial jet is 210 miles per hour faster than the speed of the private airplane. Find the speed of both airplanes.
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Holly Schmidt
Le the distance to be covered be x miles speed of commercial jet ${S}_{cj}=\frac{x}{1\cdot 1}\phantom{\rule{0ex}{0ex}}x=1\cdot 1{S}_{cj}$
Speed of private plane ${S}_{pp}=\frac{x}{1.8}\phantom{\rule{0ex}{0ex}}1.1{S}_{cj}=1.8{S}_{pp}$
Given that S is 210 miles/hr faster than S_pp
Substitute
$\frac{1.8}{1.1}{S}_{pp}=210+{S}_{pp}\phantom{\rule{0ex}{0ex}}\left(1.8-1\right){S}_{pp}=210\phantom{\rule{0ex}{0ex}}\frac{7}{11}{S}_{pp}=210\phantom{\rule{0ex}{0ex}}{S}_{pp}=\frac{30×11}{7}=330\phantom{\rule{0ex}{0ex}}{S}_{cj}=210+{S}_{pp}=210+330=540$