The side area of a cylinder is 188.4 square decimeters, and the bottom radius is 4 decimeters. How many decimeters is its height?

high
=Side area / perimeter of bottom surface
=188.4÷（2×3.14×4）
=7.5 decimeters

The side area of a cylinder is 188.4dm2, and its bottom radius is 2DM. What is its height?

188.4 ÷ (2 × 3.14 × 2) = 188.4 ÷ 12.56 = 15 (decimeter) a: its height is 15 decimeters

Known (2005-a) (2003-a) = 1000, please guess (2005-a) 2 + (2003-a) 2=______ ．

From the theme, (2005-a) 2 + (2003-a) 2 = [(2005-a) - (2003-a)] 2 + 2 (2005-a) (2003-a), so we can get (2005-a) 2 + (2003-a) 2 = 4 + 2 × 1000 = 2004

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