Page 163 - Start Up Mathematics_3

Solution: The rows of the grid are named 1, 2, 3, ..., 8 and the columns A, B, C, ..., I.

The first shape drawn in the grid is a triangle. Let’s read the position
of its vertices. To do so, we see the row and the column in which the
point falls. Here, the first vertex lies in the first row and column C. So

we write it as (1, C). Similarly, the other vertices are (3, A) and (3, E).
The second shape in the grid is a square. The positions of its 4 vertices
are (5, F) (5, H) (7, F) and (7, H).

Corners, Edges and Faces of Solid Figures

We know that a figure with length, width and height is known as a solid shape. Such

figures are also known as three-dimensional or 3D shapes. Let’s revise some terms
related to solid shapes.
Face: The surface of a solid shape is called its face. Mental Maths

Edge: The side where 2 faces meet is known as an What figure do you get when
edge. you join 2 cubes of edge 3 cm?

Vertex: The point where 2 edges meet is called a
vertex.

Now let’s learn about some common solid figures.

Number and Number and shape Number of
Solid shape
shape of faces of edges vertices

vertex Cube

face
1. 6, square 12, straight 8

edge

Cuboid edge

vertex 6, rectangle 12, straight 8
2. face

Sphere
curved face
3. 1, curved 0 0

contd…

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