Let ABCD be the rectangle of length l units and width w units.
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Now, we construct a triangle of maximum area inside it in all possible ways.
We know that,
Area of triangle =12×Base×Height
So, for maximum area, base and height of maximum lengths are needed.
Maximum base length =l
Maximum height length =w (1 mark)
∴ Area (maximum) of triangle =12×l×w=l×w2 sq units (1 mark)