Find the area of a triangle whose sides are 3 cm, 4 cm and 5 cm.

Find the area of a triangle whose sides are 29 cm, 20 cm and 21 cm.

Find the area of a triangle whose sides are 34 cm, 20 cm and 42 cm. Hence, find the length of the altitude corresponding to the shortest side.

The sides of a triangular field are 975 m, 1050 m and 1125 m. If this field is sold at the rate of ₹ 1000 per hectare, find its selling price.