Travels Around the World

The more of this there is, the less you see. 

What is it?

Guess what comes next in the sequence:

1 2 3 4 5 ? 

The answer is not 6. What is the answer?

I am the seventh planet from the sun.

I have 27 moons. My nick name is "Ice Giant".

Who am I?

When you want to use me, you throw me away. 

When you're done using me, you bring me in. 

What am I?

Think of a number

Step 1: Multiply it by 3

Step 2: Add 6

Step 3: Divide by 3

Step 4: Subtract the number chosen in step one from the answer in step 4.

What is the answer?