Question:
Find the missing term in the series:
1, 2, ?, 20, 45
श्रृंखला में लुप्त पद ज्ञात कीजिए:
1, 2, ?, 20, 45
Options:
- 5
- 6
- 7
- 8
- 5
- 6
- 7
- 8
Correct Answer: c)
Explanation:
First differences: \(2 – 1 = 1\), \(7 – 2 = 5\), \(20 – 7 = 13\), \(45 – 20 = 25\).
Second differences: \(5 – 1 = 4\), \(13 – 5 = 8\), \(25 – 13 = 12\) (multiples of 4).
Hence, the missing term is 7.
पदों का अंतर: 1, 5, 13, 25।
द्वि-स्तरीय अंतर: 4, 8, 12 (4 का पहाड़ा)। अतः लुप्त पद 7 है।