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Q4(iii):
Which of the following are APs ? If they form an AP, find the common difference $d$ and write three more terms. (iii) – 1.2, – 3.2, – 5.2, – 7.2, . . .

Solution :

Given: A sequence of numbers: $-1.2, -3.2, -5.2, -7.2, \dots$

To find:
1. Determine if the given sequence forms an Arithmetic Progression (AP).
2. If it is an AP, find the common difference $d$.
3. Write the next three terms of the sequence.

Step 1: Definition of an Arithmetic Progression
A sequence $a_1, a_2, a_3, \dots, a_n$ is an Arithmetic Progression if the difference between consecutive terms is constant. This constant is called the common difference $d$, defined as:
$d = a_{n} - a_{n-1}$ for all $n > 1$.

Step 2: Calculating differences between consecutive terms
Let the given terms be:
$a_1 = -1.2$
$a_2 = -3.2$
$a_3 = -5.2$
$a_4 = -7.2$

Calculate the differences:
$d_1 = a_2 - a_1 = (-3.2) - (-1.2) = -3.2 + 1.2 = -2.0$
$d_2 = a_3 - a_2 = (-5.2) - (-3.2) = -5.2 + 3.2 = -2.0$
$d_3 = a_4 - a_3 = (-7.2) - (-5.2) = -7.2 + 5.2 = -2.0$

Step 3: Verification
Since $d_1 = d_2 = d_3 = -2.0$, the difference between consecutive terms is constant.
[Since the common difference is constant, the sequence is an AP.]

Step 4: Finding the next three terms
To find the next terms, we add the common difference $d = -2.0$ to the last known term ($a_4 = -7.2$).

Fifth term ($a_5$):
$a_5 = a_4 + d = -7.2 + (-2.0) = -9.2$

Sixth term ($a_6$):
$a_6 = a_5 + d = -9.2 + (-2.0) = -11.2$

Seventh term ($a_7$):
$a_7 = a_6 + d = -11.2 + (-2.0) = -13.2$

Final Answer:
The sequence forms an AP.
The common difference $d = -2.0$.
The next three terms are -9.2, -11.2, and -13.2.


More Questions from Class 10 Mathematics Arithmetic Progression EXERCISE 5.1


CBSE Solutions for Class 10 Mathematics Arithmetic Progression


Chapters in CBSE - Class 10 Mathematics


Other Subjects in CBSE - Class 10

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