  # Important Questions for CBSE Class 11 Maths Chapter 9 - Sequences and Series

## CBSE Class 11 Maths Chapter-9 Important Questions - Free PDF Download

Free PDF download of Important Questions with solutions for CBSE Class 11 Maths Chapter 9 - Sequences and Series prepared by expert Maths teachers from latest edition of CBSE(NCERT) books. CoolGyan.Org to score more marks in your Examination.

4 Marks Questions

3.Find the sum to n terms of the series 33 ​ 34

Ans.an = 12 + 22 + 32 + --- +n2

35 ​ 36 37 ​ 38 39 ​ 40 41 ​ 42 43 ​ 44 45 ​ 46 47 ​ 48 49 ​ 50

51

4.Show that the sum of (m+n)th and (m-n)th terms of an A. P. is equal to twice the mth term.

52 ​ 53

Ans. am+n = a + (m+n-1) d

54 ​

6 Marks Questions

1. 150 workers were engaged to finish a job in a certain no. of days 4 workers dropped out on the second day, 4 more workers dropped out on the third day and so on. It took 8 more days to finish the work find the no. of days in which the work was completed

Ans. a = 150, d = -4 If total works who would have worked all n days 150(n-8) 2.  Prove that the sum to n terms of the series Ans. Sn = 11 + 103 + 1005 + ---- + n terms

Sn = (10+1) + (102 + 3) + (103 + 5) + ----- + [10n + (2n-1)]  3. The ratio of A M and G. M of two positive no. a and b is m : n show that Ans.      Sq both side  4. Between 1 and 31, m number have been inserted in such a way that the resulting sequence is an A.P. and the ratio of 7th and (m-1)th no. is 5:9 find the value of m.

Ans.        5. The Sum of two no. is 6 times their geometric mean, show that no. are in the ratio (3 + 3 2) : (3 – 2 2)

Ans.           