Can someone me understand how to do these

1)

you can think of the cup's sleeve as a cylinder with say a height of 4 and a diameter of 5.  Now, if the diameter is 5 inches, the radius is half that, or 2.5,



2)

same here, you can think of the tire as a cylinder, since it's a cylindrical tire, with a height of 8 and a diameter of 29, therefore a radius of 14.5,



now, that's how much spaces it covers one time only, so 5 times around is just 5 times that much.

3)

same goes for the mugs,



4)

and the same goes for the can of peas, which is also a cylinder,

a)

 

b)

the label is only the sides, and thus only the lateral area,