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Visualising Solid Shapes

Question

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An icosahedron is having 20 triangular faces and 12 vertices. Find the number of its edges.

Solution

Here:
Number of faces (F) = 20
Number of vertices (V) = 12
Let the number of edges be E.
∴ Using Euler's formula, we have
F + V = E + 2
$rightwards double arrow$ 20 + 12 = E + 2
$rightwards double arrow$ 32 = E + 2
$rightwards double arrow$ E = 32 - 2 = 30
Thus, the required number of edges = 30.

Some More Questions From Visualising Solid Shapes Chapter

For the given solid, identify the top view, front view and side view.

Draw the front view, side view and top view of the given objects.

Look at the hut and draw its front view, side view and the top view.

In the figure, a brick is given. Draw its front view, side view and top view.

Following solids are made by joining cubes. Draw their different views.

Look at the given map of a city.

Answer the following.
(a) Colour the map as follows: Blue-water, red-fire station, orange-library, yellow-schools. Green-park, Pink-College, Purple-Hospital, Brown-Cemetery.
(b) Mark a green ‘X’ at the intersection of Road ‘C’ and Nehru Road, Green ‘Y’ at the intersection of Gandhi Road and Road A.
(c) In red, draw a short street route from library to the bus depot.
(d) Which is further east, the city park or the market?
(e) Which is further south, the primary school or the Sr. Secondary School?

Draw a map of your class using proper scale and symbols for different objects.

Draw a map of your school compound using proper scale and symbols for various features like play ground main building, garden, etc.

Draw a map giving instructions to your friend so that she reaches your house without any difficulty.

What happens to F, V and E if some parts are sliced off from a solid? (To start with, you may take a plasticine cube, cut a corner off and investigate).

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