Answer:
It'd take approximately 6543 asteroids.
Step-by-step explanation:
In order to calculate the number of asteroids needed to make that planet we first need to determine the volume of each object. To do this we will consider them as spheres and apply the appropriate formula:
![V_(asteroid) = (4*\pi*0.98)/(3) = 4.11 \text{ km}^3](https://img.qammunity.org/2021/formulas/physics/college/o8w5fyx5pges2q2a6rd38inwkremgkbofz.png)
![V_(planet) = (4*\pi*6420)/(3) = 26892.03 \text{ km}^3](https://img.qammunity.org/2021/formulas/physics/college/tvclno13nfzfi99zf16497s5dk3fxbt2ep.png)
The number of asteroids needed are given by the division of planet's volume by the asteroid's volume.
![n = (26892.03)/(4.11) = 6543.07](https://img.qammunity.org/2021/formulas/physics/college/qixfc3ckqz4d7u3po7ij0ixr7xsrqquxcg.png)
It'd take approximately 6543 asteroids.