Page 209 - ICSE Math 5

We can identify the pattern rule by drawing dots that form a square.

1 × 1 = 1 2 × 2 = 4 3 × 3 = 9 4 × 4 = 16

Observe that the pattern is obtained when a number is multiplied by itself.
The sum of any two consecutive triangular numbers is a square number. For example, 1 + 3 = 4
(square number), 3 + 6 = 9 (square number), and so on.

Exercise 15.4

1. Write the triangular or square numbers shown by the dots in the given triangular and
square patterns.

(a) (b) (c) (c)

2. Find the next two triangular numbers for the given sequence.

1, 3, 6, 10, 15, 21, __, __

3. Find the next two square numbers for the given sequence.

1, 4, 9, 16, __, __

Review Exercise

1. Observe and complete the following patterns.
(a) 3, 5, 8, 12, 17, ___, ___, ___, ___

(b) 10, 20, 35, 55, 80, ___, ___, ___, ___

(c) _______ _______

(d) _______ _______ _______

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