Q14 of 55 Page 1

In Fig. 10, ABC is a triangle right-angled at B, with AB = 14 cm and BC = 24 cm. With the vertices A, B and C as centers, arcs are drawn, each of radius 7 cm. Find the area of the shaded region. [Use π = 22/7]

Base of the tringle = BC = 24 cm


Height of the triangle = BA = 14 cm


Therefore, Area of the triangle ABC = 1/2 × Base × Height


= 1/2 × 24 × 14


= 168 cm2


Radius of each sector = r = 7 cm.


AB = 18 cm, DC = 32 cm


Distance between AB and DC = Height = 14 cm


Now, Area of the trapezium = (1/2) × (Sum of parallel sides) × Height


= (1/2) × (18 + 32) × 14 = 350cm2


As AB DC, A + D = 180°


and B + C = 180°


Also, radius of each arc = 7 cm


Therefore,


Area of the sector with central angle A = (1/2) × (A/180) × π × r2


Area of the sector with central angle B (1/2) × (B/180) × π × r2


Area of the sector with central angle C = (1/2) × (C/180) × π × r2


Total area of the sectors =



( Sum of all angles of a triangle is 180°)


= 77 cm2


Area of shaded region = Area of triangle – (Total area of sectors)


= 168 – 77 = 91 cm2


Hence, the required area of shaded region is 91 cm2.


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