12.For his autumn break, Manu was told by
his science teacher to make a model of a
rectangular pyramid as shown below. He
decided to make model of his house for his
holiday homework. He did so by using glue,
glass sheets and scissors. He put coloured
tape around each edge. Measurement of
each edge shown in the figure is in inches.
(a) How much coloured tape will be
required to put around all edges? (b) What
is the area of the bottom face in (c) How
many triangles are there ? feet? (1foot =
12inches) (d) What will be the length of
coloured tape required for the house, if we
decrease the height by 3 inches?(e)
Complete the following w.r.t. the given
model of rectangular pyramid : (i) Faces =
(ii) Edges = (iii) Vertices =
13
13
13
4
10
Answers
Given : Manu was told by his science teacher to make a model of a rectangular pyramid
He did so by using glue, glass sheets and scissors. He put coloured tape around each edge.
To Find : a) How much coloured tape will be required to put around all edges?
(b) What is the area of the bottom face in________feet? (1foot = 12inches)
(c) How many triangles are there ?
(d) What will be the length of coloured tape required for the house, if we decrease the height by 3 inches?
(e) Complete the following w.r.t. the given model of rectangular pyramid :
(i) Faces = ______ (ii ) Edges =______ (iii) Vertices =______
Solution:
coloured tape will be required to put around all edges
= 2 ( 10 + 4) + 4 * 13
= 28 + 52
= 80 inches
Area of bottom Face = 10 * 4 = 40 sq inches
in sq feet = (10/12) * (4/12) = 40/144 = 5/18 sq feet
4 triangles are there
length of coloured tape required for the house, if we decrease the height by 3 inches
( assuming edge length of triangle reduced by 3 inches )
= 2 ( 10 + 4) + 4 * (13 - 3)
= 28 + 40
= 68 inches
(i) Faces = 5 (ii ) Edges = 8 (iii) Vertices = 5
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