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Sequences and Series — CBSE Class 11

Master Sequences and Series for CBSE Class 11. Free verified step-by-step solutions, 3 past exam problems, formulas, and markschemes.

Exam Questions & Step-by-Step Markschemes (3 Problems)

Question 1 • 2024 4 Marks
Find the sum to n terms of the sequence: 7, 77, 777, 7777, \dots
Answer: S_n = \frac{70}{81}(10^n - 1) - \frac{7n}{9}
Question 2 • 2024 4 Marks
Find the sum to n terms of the series: S_n = 8 + 88 + 888 + 8888 + \dots \text{ to } n \text{ terms}
Answer: S_n = \frac{80}{81}(10^n - 1) - \frac{8n}{9}
Question 3 • 2023 5 Marks
Find the sum to n terms of the series: 1 \cdot 2 + 2 \cdot 3 + 3 \cdot 4 + 4 \cdot 5 + \dots
Answer: S_n = \frac{n(n + 1)(n + 2)}{3}

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