The length and breadth of a rectangular solid are respectively 25 cm and 20 cm. If the volume is 7000 cm³, find its height.

Mary wants to decorate her Christmas tree. She wants to place the tree on a wooden box covered with coloured papers with pictures of Santa Claus. She must know the exact quantity of paper to buy for this purpose. If the box has length 80 cm, breadth 40 cm and height 20 cm respectively, then how many square sheets of paper of side 40 cm would she require?

A class room is 10 m long, 6 m broad and 4 m high. How many students can it accommodate if one student needs 1.5 m² of floor area? How many cubic metres of air will each student have?

The perimeter of one face of a cube is 20 cm. Find the surface area and the volume of the cube.