Question

Find area of rectangle ABCD Angle A = 90° AB=16cm AD=12cm BC=CD=12.5cm

​

Answer 1

Area of △ABD=

2

1

×AB×AD

∴Area of △ABD=

2

1

×16×12

=96cm

2

△ABD is a right angled triangle.

∴BD

2

=AB

2

+AD

2

=16

2

+12

2

=256+144

=

400

=20cm

Now in △BCD, using Heron's formula,

S=

2

BC+DB+CD

=

2

12.5+20+12.5

=

2

45

=22.5

Area of △BCD=

s(s−BC)(s−CD)(s−DB)

=

22.5(22.5−12.5)(22.5−12.5)(s−20)

=75cm

2

Area of quadrilateral ABCD= Area of △BCD+Area of △ABD

=(75+96)

=171cm

2