NCERT Class X Chapter 5: Arithmetic Progression Example 2 (iv)

NCERT Class X Chapter 5: Arithmetic Progression Example 2(iv)

Question:

Which of the following list of numbers form an AP? If they form an AP, write the next two terms 1, 1, 1, 2, 2, 2, 3, 3, 3, . . .

Given:

The sequence: 1, 1, 1, 2, 2, 2, 3, 3, 3, . . .

To Find:

Whether the given sequence forms an arithmetic progression (AP). If it does, find the next two terms.

Formula:

In an AP, the difference between consecutive terms is constant (common difference).

Solution:

Let the given list of numbers be a1, a2, a3, a4, ...

Then,
a1 = 1 

a2 = 1 

a3 = 1

a4 = 2

a5 = 2

a6 = 2

a7 = 3

a8 = 3

a9 = 3 

Lets calculate the common difference,

d = a2 - a1 = 1 - 1 = 0

d = a3 - a2 = 1 - 1 = 0

d = a4 - a3 = 2 - 1 = 1

The common difference changes and hence it is not a constant. 

Hence, the sequence is not an AP because the difference between consecutive terms is not constant. 

Result:

The given sequence 1, 1, 1, 2, 2, 2, 3, 3, 3, . . . is not an arithmetic progression. 

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