Question

if earth were to shrink suddenly shrinks so that its radius becomes 1/3rd of its

Answer 1

total radius of earth =6400

if it shrinks then the radius will be

$6400 - \frac{1}{3} \\ \frac{6400 \times 3 - 1}{ 3} \\ \frac{19200 - 1}{3} \\ \frac{19199}{3} \\ = 6,399.66667$