Adv
deepaksoni
  • 0
Guru

Question 10. In a certain A.P. the 24th term is twice the 10th term. Prove that the 72nd term is twice the 34th term

  • 0

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 in a certain A.P. the 24th term is twice the 10th term.

Now we have to prove that the 72nd term is twice the 34th term

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

Share

1 Answer

  1. Solution: 

    Given that,

    24th term is twice the 10th term.

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

    a24 = 2(a10)

    a + (24 – 1)d = 2(a + (10 – 1)d)

    a + 23d = 2(a + 9d)

    a + 23d = 2a + 18d

    a = 5d …. (1)

    Now, the 72nd term can be expressed as:

    a72 = a + (72 – 1)d

    = a + 71d

    = a + 5d + 66d

    = a + a + 66d [using (1)]

    = 2(a + 33d)

    = 2(a + (34 – 1)d)

    = 2(a34)

    ⇒ a72 = 2(a34)

    Hence, the 72nd term is twice the 34th term of the given A.P.

    • 0
Leave an answer

Leave an answer

Browse

Choose from here the video type.

Put Video ID here: https://www.youtube.com/watch?v=sdUUx5FdySs Ex: "sdUUx5FdySs".

Captcha Click on image to update the captcha.

Related Questions