Ncert solution for class 11 mathematics chapter - 9 SEQUENCES AND SERIES

## Exercise 9.1

- Ncert Solution Class 11 question 1 to 6
- Ncert Solution for class 11 question 7 to 10
- Ncert Solutions for exercise 9.1 question 11 to 13
- Ncert solution question 14

## Exercise 9.2

- Find the sum of odd integers from 1 to 2001.
- Find the sum of all natural numbers lying between 100 and 1000, which aremultiples of 5.
- In an A.P., the first term is 2 and the sum of the first five terms is one-fourth ofthe next five terms. Show that 20th term is –112.
- How many terms of the A.P. – 6, 112− , – 5, … are needed to give the sum –25?
- In an A.P., if pth term is 1qand qth term is 1p, prove that the sum of first pqterms is 12(pq +1), where p ≠ q.
- If the sum of a certain number of terms of the A.P. 25, 22, 19, … is 116. Find thelast term.
- Find the sum to n terms of the A.P., whose kth term is 5k + 1.
- If the sum of n terms of an A.P. is (pn + qn2), where p and q are constants,find the common difference.
- The sums of n terms of two arithmetic progressions are in the ratio5n + 4 : 9n + 6. Find the ratio of their 18th terms.
- If the sum of first p terms of an A.P. is equal to the sum of the first q terms, thenfind the sum of the first (p + q) terms.
- Sum of the first p, q and r terms of an A.P are. a, b and c, respectively.Prove that a (q r) b (r p) c ( p q) 0p q r− + − + − =12. The ratio of the sums of m and n terms of an A.P. is m2 : n2. Show that the ratioof mth and nth term is (2m – 1) : (2n – 1).
- If the sum of n terms of an A.P. is 3n2 + 5n and its mth term is 164, find the valueof m.
- Insert five numbers between 8 and 26 such that the resulting sequence is an A.P.
- If 1 1n nn na ba − b −++is the A.M. between a and b, then find the value of n.
- Between 1 and 31, m numbers have been inserted in such a way that the resultingsequence is an A. P. and the ratio of 7th and (m – 1)th numbers is 5 : 9. Find thevalue of m.
- A man starts repaying a loan as first instalment of Rs. 100. If he increases theinstalment by Rs 5 every month, what amount he will pay in the 30th instalment?
- 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.