If R is radius of the earth and g the acceleration due to gravity on the earth’s surface, the mean density of the earth is
$\dfrac{4\pi G}{2gR}$
$\dfrac{3\pi G}{4gR}$
$\dfrac{3g}{4\pi RG}$
$\dfrac{4\pi RG}{3g}$
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The masses of two planets are in the ratio 1 : 2. Their radii are in the ratio 1 : 2. The acceleration due to gravity on the planets are in the ratio.