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# Lecture - 4 Chapter 9 Sequences & Series

NCERT EXERCISE 9.2 |

**Question 13.** If the sum of n terms of an A.P. is \( 3n^2+5n\) and its *m*^{th} term is 164, find the value of *m*.

**Question 14.** Insert five numbers between 8 and 26 such that the resulting sequence is an A.P.

**Question 15.** If \( \frac{a^n+b^n}{a^{n-1}+b^{n-1}} \) is the A.M. between *a* and *b*, then find the value of *n*.

**Question 16.** Between 1 and 31, *m* numbers have been inserted in such a way that the resulting sequence is an A. P. and the ratio of 7^{th }and (*m* – 1)^{th} numbers is 5 : 9. Find the value of *m*.

**Question 17.** A man starts repaying a loan as first installment of Rs. 100. If he increases the installment by Rs 5 every month, what amount he will pay in the 30^{th} installment?

**Question 18.** The difference between any two consecutive interior angles of a polygon is 5°. If the smallest angle is 120° , find the number of the sides of the polygon.