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,

then we have to find n and Sn,

Where a = 5, d = 3 and an = 50.

CBSE DHANPAT RAI publication

CBSE Mathematics Class 10th

Question 56(i)

Given A.P. has a = 5, d = 3 and a

_{n}= 50.By using the formula of nth term of an A.P.a_{n}= a + (n – 1)dSo,=> 50 = 5 + (n – 1)3

=> 3(n – 1) = 45

=> n – 1 = 15

=> n = 16

Now by using the formula of sum of n terms of an A.P.S_{n}= n[a + a_{n}] / 2So,S

_{16}= 16[5 + 50] / 2= 8[55]

= 440

Hence, the value of n is 16 and sum is 440.