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SAI International School
CLASS - X

Mathematics

CHAPTER-12: Surface Areas and Volumes
Lab Activity-2

SUBTOPIC: Surface Area of Cone

Surface Area of a Cone

Objective
To find the formula for the lateral surface area and total surface area of a right circular
cone experimentally.

Prerequisite Knowledge

1. Area of circle =
2. Area of parallelogram = b x h (b =base, h = height).
3. Circumference of circle =

Materials Required
A cone made of chart paper, a pair of scissors, geometry box, fevicol, cello tape.

Procedure

1. Make a cone of pink chart paper having base radius r, slant height ‘l’ and height h.
2. Cut the cone along slant height as shown in fig (i) as per dotted line and unroll it
to get a sector, as shown in fig. (ii). Name this sector OAB.
3. Identify the arc length AB of the sector OAB = circumference of the base of the
cone. radius of the sector OAB = slant height of the cone. As shown in the fig. (ii).
4. Cut the sector OAB into 4 small equal sectors, along dotted lines as shown in fig.
(ii) and fill red colour in two sectors as shown.
5. Arrange these small sectors to get a parallelogram as shown in fig. (iii).