a5= a + (n -1) d2 = -14 + 4d16 = 4dd = 4Sn = [2a + (n – 1) d]40 = [2(-14) + (n -1) (4)]40 = 12n2 – 16n2n2 – 16n -40 = 0n2 – 8n -20 = 0n2 – 10n + 2n – 20 = 0(n – 10) (n + 2) = 0n = 10 and n = -2 (not possible)

1 2 3 4 5 A 5 B 5 C 5 D 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

RD Sharma - Mathematics

Exercise 9.1

1 2 3

Exercise 9.2

1 2 3 4 5 6 7 8 9 10 11 12

Exercise 9.3

1 2 A 2 B 2 C 2 D 2 E 3 A 3 B 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Exercise 9.4

1 2 3 4 5 6 7 8

Exercise 9.5

CCE - Formative Assessment

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

Q. 5 B

How many terms ar

Class 10th RD Sharma - Mathematics 9. Arithmetic Progressions

Answer :

a₅= a + (n -1) d

2 = -14 + 4d

16 = 4d

d = 4

S_n = [2a + (n – 1) d]

40 = [2(-14) + (n -1) (4)]

40 = 12n² – 16n

2n² – 16n -40 = 0

n² – 8n -20 = 0

n² – 10n + 2n – 20 = 0

(n – 10) (n + 2) = 0

n = 10 and n = -2 (not possible)

Rate this question :

How useful is this solution?

We strive to provide quality solutions. Please rate us to serve you better.

PREVIOUSHow many terms of NEXTHow many terms of

Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts

Dedicated counsellor for each student

24X7 Doubt Resolution

Daily Report Card

Detailed Performance Evaluation

view all courses