Answer: [tex]5\times 10^7\ \text{years}[/tex]
Explanation:
Given
A Planet is moving at a rate of 3 cm/year
distance between planets is 1500 km
and 1 km=1000 m
1 m=100 cm
No. of years required to cover 1500 km=[tex]\dfrac{1500\times 1000\times 100}{3}=5\times 10^7\ \text{years}[/tex]