One of the most important and exam oriented question from Chapter name- Arithmetic Progression
Class 10th
Chapter number- 9
Exercise :- 9.6
This type of question has been asked in previous years exams.
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 a
Where an = 28, Sn = 144 and n = 9
CBSE DHANPAT RAI publication
CBSE Mathematics Class 10th
Question 56(iv)
Given A.P. has an = 28, Sn = 144 and n = 9.
Now by using the formula of sum of n terms of an A.P.
Sn = n[a + an] / 2
So,
=> 144 = 9[a + 28] / 2
=> a + 28 = 32
=> a = 4
Hence, the value of a is 4.