distance to the center of the earth math/science

Question

the distance from the surface of the earth to the center is 6,371 km, if you were to make a model of the earth and from the outside to the center was 9.9 cm, 1 cm = _______ km

Answer 1

Think of it as a proportion problem:

 

6371 km is to 9.9 cm as x km is to 1 cm.

 

6371 / 9.9 = x / 1

 

So x = 6371 / 9.9 = 643.5