1. Introduction – परिचय
English: In our daily life, we often come across number patterns such as:
- 2, 4, 6, 8, 10, …
- 5, 10, 15, 20, …
- 100, 90, 80, 70, …
These number patterns follow a fixed rule. Such patterns are called sequences. If the difference between consecutive terms is constant, the sequence is called an Arithmetic Progression (A.P.).
हिंदी: हमारे दैनिक जीवन में कई संख्यात्मक क्रम मिलते हैं। यदि किसी क्रम में प्रत्येक दो क्रमागत पदों का अंतर समान हो, तो ऐसे क्रम को समांतर श्रेढ़ी कहते हैं।
2. Arithmetic Progression (A.P.) – समांतर श्रेढ़ी
English: An Arithmetic Progression is a sequence in which the difference between any two consecutive terms is constant.
हिंदी: समांतर श्रेढ़ी वह श्रेढ़ी है जिसमें प्रत्येक क्रमागत दो पदों के बीच का अंतर समान रहता है।
Examples:
- 3, 7, 11, 15, …
- 10, 8, 6, 4, …
- -2, 0, 2, 4, …
Non-Examples:
- 2, 4, 8, 16
- 1, 4, 9, 16
3. General Form of an Arithmetic Progression – सामान्य रूप
The general form of an A.P. is:
where:
- a = first term (प्रथम पद)
- d = common difference (सार्व अंतर)
4. First Term of an A.P. – प्रथम पद
English: The first number of an arithmetic progression is called its first term and is denoted by a.
हिंदी: समांतर श्रेढ़ी के पहले पद को प्रथम पद कहते हैं।
Example: In A.P. 5, 9, 13, 17, …
First term, a = 5
5. Common Difference of an A.P. – सार्व अंतर
English: The common difference is the difference between any term and the term just before it.
Example: In A.P. 10, 7, 4, 1, …
d = 7 − 10 = −3
6. nth Term of an Arithmetic Progression – nवाँ पद
English: The term at position n in an arithmetic progression is called the nth term.
हिंदी: समांतर श्रेढ़ी में nवें स्थान पर स्थित पद को nवाँ पद कहते हैं।
7. Formula for nth Term of an A.P. – nवें पद का सूत्र
- an = nth term
- a = first term
- d = common difference
- n = term number
Example:
Find the 10th term of A.P. 2, 5, 8, …
a = 2, d = 3, n = 10
a10 = 2 + (10 − 1) × 3 = 29
8. Sum of First n Terms of an A.P. – प्रथम n पदों का योग
English: The sum obtained by adding the first n terms of an arithmetic progression is called the sum of first n terms.
हिंदी: समांतर श्रेढ़ी के पहले n पदों के योग को प्रथम n पदों का योग कहते हैं।
9. Formula for Sum of First n Terms – योग का सूत्र
Formula 1:
Formula 2:
- Sn = sum of first n terms
- a = first term
- d = common difference
- l = last term
Example:
Find the sum of first 20 terms of A.P. 3, 7, 11, …
S20 = 820
10. Word Problems based on Arithmetic Progressions – कथनात्मक प्रश्न
English: Many real-life problems can be solved using arithmetic progressions such as savings, distance, salary, seating arrangements, etc.
हिंदी: समांतर श्रेढ़ी पर आधारित प्रश्न दैनिक जीवन से जुड़े होते हैं जैसे बचत, दूरी, वेतन वृद्धि आदि।
Steps to Solve:
- Identify the A.P.
- Find values of a, d, and n
- Apply the correct formula
- Write the final answer clearly