# CBSE 11 Math Practice Paper 9 Sequences and Series

(i) \(a_n = 3n + 5\) (ii) \(a_n = \frac{n−4}{3}\)

2. What is the \(20^{th}\) term of the sequence defined by \(a_n = (n – 1) (2 – n) (3 + n)\)?

3. Find the \(10^{th}\) and \(n^{th}\) terms of the G.P. 5, 25, 125, ..… .

4. Which term of the G.P., 2,8,32, ... up to n terms is 131072?

5. In a G.P., the 3rd term is 24 and the 6th term is 192.Find the 10th term.

6. How many terms of the G.P. 3 3 32 4 , , ,... are needed to give the sum \(\frac{3069}{512}\)?

7. The sum of first three terms of a G.P. is \(\frac{13}{12}\) and their product is – 1. Find the common ratio and the terms.

8. Find the sum of the sequence 7, 77, 777, 7777, ... to n terms.

9. If A.M. and G.M. of two positive numbers a and b are 10 and 8, respectively, find the numbers.

10. Evaluate \(\sum_{k=1}^{11} (2 + 3^k)\)

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