<h2>
Answer:</h2>
Hence, the number of times will Gus need to fill the bucket to completely fill the fish tank if he doesn't spill a drop is:
3 times
<h2>
Step-by-step explanation:</h2>
The amount of water that a tank can hold is: 4710 inches cube.
This means that the volume of tank is: 4710 cubic inches.
Also, the bucket is in the shape of a cylinder with radius 5 inches and height 20 inches.
This means that the Volume of bucket is given by:

where r denotes radius and h denotes height.
Hence, Volume of bucket is:

Let n be the number of times Gus need to fill the bucket to completely fill the fish tank
Hence, we have:
Volume of fish tank= n × Volume of Bucket
i.e. 
Hence, the answer is:
3