This is the Important question based on Arithmetic progression Chapter of R.S Aggarwal book for ICSE & CBSE
Board.
Here the AP and the last term of AP is given you have to find which term of the AP this must be.
This is the Question Number 9 Exercise 11 A of RS Aggarwal Solution.
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Which term of the AP 3, 8, 13, 18, … is 88?
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Let nth term is 88.
AP is 3, 8, 13, 18, …
Here,
First term = a = 3
Common difference = d = 8 – 3 = 5
nth term of AP is a_n = a + (n – 1) d
Now,
88 = 3 + (n – 1)(5)
88 – 3 = (n – 1) x 5
n – 1 = 88 /5
or n = 17 + 1 = 18
Therefore: 88 is the 18th term.