Ch 11 extends mensuration to areas of trapeziums, general quadrilaterals, and polygons, and introduces surface area and volume of 3D shapes: cube, cuboid, and cylinder.
Trapezium: area = ½ × (sum of parallel sides) × height. General quadrilateral: split into triangles using a diagonal. Rhombus: area = ½ × d₁ × d₂ (product of diagonals). Any polygon can be divided into triangles for area computation.
Cube: total surface area = 6a². Cuboid: TSA = 2(lb + bh + hl). Cylinder: curved surface area = 2πrh, TSA = 2πr(r+h). Lateral surface area excludes top and bottom.
Volume of cube = a³. Volume of cuboid = l × b × h. Volume of cylinder = πr²h. Volume measures the space occupied by a 3D object, expressed in cubic units.
Download: https://ncert.nic.in/textbook/pdf/hemh111.pdf | Complete book: https://ncert.nic.in/textbook/pdf/hemh1ps.zip
Surface area is the total area of all faces/surfaces of a 3D shape (measured in sq. units). Volume is the space enclosed inside (measured in cubic units). Surface area is like the wrapping; volume is the capacity.
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