Guru

# Question 43. The sum of first q terms of an A.P. is 63q – 3q2. If its pth term is –60, find the value of p. Also, find the 11th term of this A.P.

• 0

This is the basic and conceptual question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise 9.6

In this question we have been given that The sum of first q terms of an A.P. is 63q – 3q2.

Also it is given that  its pth term is –60,

Now we have to find the value of p. Also,  the 11th term of this A.P.

CBSE DHANPAT RAI publications
Class:- 10th
Solutions of CBSE Mathematics
Question 43

Share

1. Given Sn = 63q – 3q2,

On putting n = 1, we get the first term(a), S1 = a = 63(1) – 3(1)2 = 60.

On putting n = 2 gives S2 = a + a + d = 63(2) – 3(2)2 = 114

=> d = 114 – 2a

=> d = 114 – 120 = –6

The pth term of the A.P., ap = a + (p – 1)d = –60

=> 60 + (p – 1)(–6) = –60

=> (p – 1)(–6) = –120

=> p – 1 = 20

=> p = 21

11th term of the A.P., a11 = a+10d

= 60 + 10(–6)

= 0

Hence, the value of p is 21 and 11th term of the A.P. is 0.

• 0