We know that parallelogram is also a quadrilateral. Let us also split such a quadrilateral into two triangles, find their areas ad hence that of the parallelogram . Does this agree with the formula that you know already?

Consider a concave quadrilateral ABCD, Split it into two triangles and find the sum of the interior angles.

Take any quadrilateral, say ABCD , Divide it into two triangles, by drawing a diagonal. You get six angles 1,2,3,4,5 and 6. Use the angle sum property of a triangle and argue how the sum of the measures of and amount to 180^@ + 180^@ = 360^@ .

Take a sheet of paper. Measure its area. Pile up such sheets of paper of same size to make cuboid. Measure the height of this pile. Find the volumne of the couboid by finding the product of the area of the sheet and the height of this pile of sheets. This activity illustrates the idea that volume of a solid can ve deduce by thsi method also (if the base and top of the solid are congruent and parallel to each other and its edges are perpendicular to the base). Can you think of such objects whose volumne can be found by using this method?

Take two concal flasks and paint one white and other black.Fill both with water. Place the conical flasks in direct sunlight for half an hour to one hour. Touch the conical flasks . Which one is hotter ? You could also measure the temperature of the water in the two conical flasks with a thermometer. Can you think of ways in which this finding could be used in your daily life ?