Question

AP consists of 40 terms is the first and the last term sa -4 and 249 respectively find the 23 rd term​

Answer 1

Answer :-

• 138.56 is the correct answer

Step-by-step explanation:

Given : An AP consists of 40 terms of which first and last term are -4 and 249

To find : 23rd term of AP

Solution :

In order to find the 23rd term, we have to find the common difference of the given AP.

Given in the question that last term of AP is 249 which is the 40th term, so :

⟶ a40 = 249

It can also be written as :

⟶ a + 39d = 249

First term of AP is -4 as given in the question, put it's value in this equation.

⟶ -4 + 39d = 249

⟶ 39d = 249 + 4

⟶ 39d = 253

⟶ d = 253 / 39

⟶ d = 6.48 approx.

We have successfully obtained the value of common difference, now apply formula for nth term of AP.

⟹ an = a + ( n - 1 ) d

Put n = 23 for 23rd term

⟹ an = -4 + ( 23 - 1 ) ( 6.48 )

⟹ an = -4 + (22) (6.48)

⟹ an = -4 + 142.56

⟹ an = 138.56