This is the Important question based on Arithmetic progression Chapter R.S Aggarwal book for ICSE & CBSE Board.
In this Question the last term of AP is given you have to find the number of terms in the given AP .
This is the Question Number 8 Exercise 11 A of RS Aggarwal Solution.
Deepak BoraNewbie
How many terms are there in the AP 41, 38, 35, …, 8?
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Given: AP is 41, 38, 35,…, 8
Here, first term = a = 41
Last term = 8
Common difference = d = 38 – 41 = -3
To find: the number of terms (n)
Last term = a + (n – 1)d
8 = 41 + (n – 1)(-3)
8 – 41 = (n – 1)(-3)
n– 1 = 11
n = 11 + 1 = 12
There are 12 terms.