NCERT Class 9 Solutions: Heron's Formula (Chapter 12) Exercise 12.2 Part 2

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Q-3 Radha made a picture of an airplane with colored paper as shown in figure. Find the total area of the paper used.

Picture of an Airplane

Picture of an airplane made with colored paper


We can divide the airplane into the separate quadrilaterals and triangles. Let’s find each of their areas

For triangle (i)

Isolated Top Triangle From the Airplane.

Isolated triangle from the airplane.

This triangle is an isosceles triangle, therefore its perimeter and semi-perimeter

By using heroes formula, area of the triangle

  • (approx.)

For quadrilateral (ii)

Rectangle in Middle Part of Aircraft

Rectangle thatlength=6.5cmandbase=1cm

Area of Rectangle

For quadrilateral (iii)

Trapezium at Tail of Aircraft

Trapezium at tail of aircraft

This quadrilateral is a trapezium. To find the area we need to first find its height. =

  • Perpendicular height of parallelogram

  • Area=area of parallelogram+ area of equilateral triangle

For triangle (IV) = triangle (v)

We know

  • (2 triangle)

Therefore, total area of the paper used