Page 57 - Mathematics Class - XI
P. 57
TOPIC - 8: Sequences and Series
ACTIVITY 8.1
OBJECTIVE
To obtain formula for the sum of squares of first n-natural numbers.
MATERIAL REQUIRED
Plastic unit cubes Nails Sketch pen
Coloured papers Glue
PRE-REQUISITE KNOWLEDGE
1. Knowledge of natural numbers 3. Knowledge of volume of cuboid
2. Knowledge of sequences
PROCEDURE
1. Take 1 (= 1 ) plastic unit cube as shown in 2. Take 4 (= 2 ) plastic unit cubes form a cuboid as
2
2
Fig. (a). shown in Fig. (b).
Fig. (a) Fig. (b)
3. Take 9 = (3 ) plastic unit cubes form a cuboid 4. Take 16 = (4 ) plastic unit cubes form a cuboid
2
2
as shown in Fig. (c). as shown in Fig. (d).
Fig. (c) Fig. (d)
5. Arrange all the cube and cuboids of Fig. (a) to (d) above so as to form an echelon type structure as shown
in Fig. (e).
+ + +
Fig. (e)
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