NCERT Class 9 Solutions: Heron's Formula (Chapter 12) Exercise 12.2 Part 5
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Q8 A floral design on a floor is made up of 16 tiles which are triangular, the sides of the triangle being (see Fig). Find the cost of polishing the tiles at the rate of
Solution:

Semi perimeter of each of the triangular shapes

Therefore, area of each of the triangular tiles


Therefore, total area of


Cost of polishing tiles =

Therefore, total cost of polishing tiles

Q9 A field is in the shape of a trapezium whose parallel sides are 25 m and 10 m. The nonparallel sides are 14 m and 13 m. find the area of the field.
Solution:
Given,

SBQP be the trapezium with parallel sides and the nonparallel sides
Construction,

Draw

Draw , therefore QPSR is now a parallelogram
In,

and

.

Therefore, semi perimeter of the
Therefore, by Herons formula, area of the
Area of the parallelogram
Therefore, area of the trapezium