0.04 is 10 of which decimal?

Can you guys plz answer this question in order and quickly plz i will give 30 points

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.

I’m on question 7 it says a covered water tank is in the shape of a cylinder the tank has a 28 inch diameter and a height of 66 inches to the nearest square inch what is the surface area of the water tank