Question 782720
parallel sides are 90 & 30

if you draw a perpendicular from the smaller side 
itdivides the opposite side into 30 and 60

there are two shapes one is a rectangle and other is a  right triangle

the right triangle has hypotenuse of 100 and one side as 60

so other side =

sqrt(100^2-60^2)= 80

the there sides of triangle are 
60,80 and 100

herons formula
area = {{{sqrt(s(s-a)(s-b)(s-c))}}}

where s= 1/2 the perimeter

s= (60+80+100)/2

=120


area = {{{sqrt(120(120-60)(120-80)(120-100))}}}

= 2400

area of rectangle = 30 * 80

=2400

area of trapezium = area of triangle + area of rectangle

=2400 +2400
=4800 sq.m