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Question 56. Let there be an A.P. with first term a and common difference d. If an denotes its nth term and Sn is the sum of first n terms, then find:(iii) d, if a = 3, n = 8 and Sn = 192

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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  there be an A.P.

first term a and common difference d.

Also, If an denotes its nth term and Sn is the sum of first n terms,

Now we have to find d, if a = 3, n = 8 and Sn = 192

CBSE DHANPAT RAI publications
Class:- 10th
Solutions of CBSE Mathematics
Question 56(iii)

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1 Answer

  1. Given A.P. has a = 3, n = 8 and S= 192.

    Now by using the formula of the sum of n terms of an A.P.

    Sn = n[2a +(n – 1)d] / 2

    So,

    => 192 = 8[2(3) + (8 – 1)d] / 2

    => 4[6+7d] = 192

    => 6+7d = 48

    => 7d = 42

    => d = 6

    Hence, the value of d is 6.

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