ABCD is a rectangle with O as any point in its interior. If ar(ΔAOD)=3cm2 and ar(ΔBOC)=6cm2, then find area of rectangle ABCD.
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Solution
Given: ABCD is a rectangle, and O is any point in its interior. Area (ΔAOD)=3 sqcm and Area (ΔBOC)=6 sq cm. From O draw a line EF parallel to AB intesecting AD at E and BC at F. Therefore OE⊥AD and OF⊥BC. Let OE =x and OF =y OE +OF=EF =AB Therefore x+y=AB ....(1) Area (ΔAOD)+ Area (ΔBOC)=3+6=9 sq. cm. 12×AD×OE+12×OF×BC=9sq.cm12[AD×OE+OF×BC]=9sq.cmAD×OE+OF×AD=9×2=18sq.cm Since BC =AD [opposite sides of a rectangle] ⇒AD(OE+OF)=18sq.cmAD×EF=18sq.cm So, EF =AB ⇒AD×AB=18sq.cm Area of the rectangle ABCD =AB×AD=18sq.cm