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Mathematical problems. . . . .
1. The surface area of a cylinder is equal to the area of two bottom surfaces plus the peripheral area of the cylinder.

Bottom area: S 1=πR square =3. 14*(4/2) square =6.28 square centimeters.

The peripheral area is equal to the perimeter of the bottom surface multiplied by the height of the cylinder.

Outer circumferential area: S2 = π dl = 3.14 * 4 * 450 = 5652cm2.

The total surface area of the cylinder is: s = 2s1+S2 = 6.28 * 2+5652 = 5664.56cm2..

2. According to the surface area calculation formula of the problem 1, we can know that:

S 1=πR square = π d square /4, perimeter = π d.

So the diameter d = 45.2/3.14 =14.39 cm.

Bottom area: s1= 3.14 *14.39 square /4= 162.55 square centimeter.

Peripheral area: S2= perimeter * height =45.2*40= 1808 cm2.

Surface area of cylinder: s = 2s1+S2 = 2133.1cm2.