# NCERT Class 9 Solutions: Heron's Formula (Chapter 12) Exercise 12.2 Part 5

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Q-8 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

Q-9 A field is in the shape of a trapezium whose parallel sides are 25 m and 10 m. The non-parallel sides are 14 m and 13 m. find the area of the field.

Solution:

Given,

SBQP be the trapezium with parallel sides and the non-parallel 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