Area of trapezium ABCD = Area of ADE + Area of Rectangle DEFC + Area of CFB
= ( 12×h×c)+(b×h) + (12×h×d)
[1 mark]
=h×[12×c + b + 12×d] =h×[c + 2×b + d2]
=h×[c + b + d + b 2]
=h×[a + b2] ∵(c+b+d=a)
[2 mark]
So,we can write the formula for the area of a trapezium
=height×[sum of parallel sides2] =12×[distance between two parallel sides ×(sum of parallel sides)]
[1 mark]