The mean radius of the earth’s around the sun is 1.5 × 10¹¹ metre. The mean radius of the orbit of mercury around the sun is 6 × 10¹⁰ metre. The mercury will rotate around the sun in

nearly ¼ years

$\frac{\mathrm{T}_{\text {mercury }}^2}{\mathrm{~T}_{\text {earth }}}=\frac{\left(6 \times 10^{10}\right)^3}{\left(1.5 \times 10^{11}\right)^3}=\left(\frac{4}{10}\right)^3$

$\frac{\mathrm{T}_{\text {mercury }}^2}{\mathrm{~T}_{\text {earth }}}=\left(\frac{4}{10}\right)^{3 / 2} ; \mathrm{T}_{\text {mercury }}=\frac{1}{4}$ year