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deepaksoni
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Asked: 2021-06-14T00:28:13+05:30 In:

Question 8. If 10 times the 10th term of an A.P. is equal to 15 times the 15th term, show that 25th term of the A.P. is zero.

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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 10 times the 10th term of an A.P. is equal to 15 times the 15th term,

Now we have to show that 25th term of the A.P. is zero.

CBSE DHANPAT RAI publications
Class:- 10th
Understanding CBSE Mathematics
Question 8

arithmetic progressionsclass 10th
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    1 Answer

    1. Guru

      Solution:

      Given that,

      10 times the 10th term of an A.P. is equal to 15 times the 15th term.

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

      10(a10) = 15(a15)

      10(a + (10 – 1)d) = 15(a + (15 – 1)d)

      10(a + 9d) = 15(a + 14d)

      10a + 90d = 15a + 210d

      5a + 120d = 0

      5(a + 24d) = 0

      a + 24d = 0

      a + (25 – 1)d = 0

      a25 = 0

      Hence, the 25th term of the A.P. is zero.

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