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deepaksoni
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Asked: 2021-06-14T00:23:07+05:30 In:

Question 5. The first term of an A.P. is 5, the common difference is 3 and the last term is 80; find the number of terms.

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This is the basic and conceptual question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise 9.4

In this question we have been given that the first term of an A.P. is 5, the common difference is 3 and the last term is 80; and we have to find the number of terms.

CBSE DHANPAT RAI publications
Class:- 10th
Understanding CBSE Mathematics
Question 5

class 10rd sharma
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    1. Guru

      Solution: 

      Given that,

      a = 5 and d = 3,

      last term = 80

      As we know that, to find nth term in an A.P = a + (n – 1)d

      therefore, for the given A.P. an = 5 + (n – 1)3 = 3n + 2

      =3n + 2 = 80

      3n = 78

      n = 78/3 = 26

      Hence, there are 26 terms in the A.P.

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