We are required to find the fraction of Earth radius is each type of crust
<em>Average radius of Earth</em> = 6,371 km
<em>Average thickness of oceanic crust</em> = 7.5 km
<em>Average thickness of continental crust </em>= 35 km
<em>fraction of Earth's radius is oceanic crust</em> = 7.5 km / 6,371 km
=
<em>fraction of Earth's radius is continental crust</em> = 35km / 6,731
=
Convert kilometer to mile
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