Page 108 - Start Up Mathematics_6

5. In each of the following statement write True or False:

(a) Any three line segments make a triangle.
(b) Every right triangle is scalene.

(c) All isosceles triangles are obtuse.
(d) A triangle may have two obtuse angles.

(e) A triangle may have two right angles.
(f) Every rectangle is a parallelogram.

(g) A rhombus is also a parallelogram.
(h) Adjacent sides of a parallelogram are equal.

6. Define a trapezium, parallelogram and a rectangle.
7. What is the difference between a regular and an irregular polygon?

Three-Dimensional Shapes
So far we have studied only two-dimensional shapes that are measured in terms of length and
breadth. Now we shall be dealing with objects having 3 dimensions, i.e., length, breadth and
height. These objects are called solids.

A polyhedron is a solid that is bounded by polygons as its faces. The segments where the faces
meet are called edges and the points where edges meet are called its vertices. Two common types
of polyhedrons are prisms and pyramids. An example of a prism is a glass slab and that of a
pyramid is a tetrahedral structure.

(i) Cube (Square prism) (ii) Triangular prism (iii) Square pyramid

(iv) Cylinder (v) Cone (vi) Sphere

• Prisms have rectangular faces as part of their lateral surface and their top and bottom are identical
polygons.
• Pyramids have triangular faces meeting at a vertex.

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