Class 09 To form a cube and find the formula for its surface area experimentally.

 Activity 26 

OBJECTIVE	MATERIAL REQUIRED
To form a cube and find the formula for	Cardboard, ruler, cutter, cellotape,
its surface area experimentally.	sketch pen/pencil.

 METHOD OF CONSTRUCTION

 1.   Make six identical squares each of side a units, using cardboard and join them as shown in Fig. 1 using a cellotape.

 Fold the squares along the dotted markings to form a cube [see Fig. 2].

DEMONSTRATION

 1.   Each face of the cube so obtained is a square of side a units. Therefore, area of one face of the cube is a² square units.

 2.   Thus, the surface area of the cube with side a units = 6a² square units.

 OBSERVATION

 On actual measurement:

 Length of side a = ..................

 Area of one square / one face = a² = ............... .

 So, sum of the areas of all the squares = ..........+............+..........+ ..........+ ..........

 + ............

Therefore, surface area of the cube = 6a²

 APPLICATION

 This result is useful in estimating materials required for making cubical boxes needed for packing.

Note: Instead of making six squares separately as done in the activity, a net of a cube be directly prepared on the cardboard itself.