Adv
deepaksoni
  • 0
Guru

Question 5. Find the sum of first 15 terms of each of the following sequences having nth term as:(iv) yn = 9 – 5n

  • 0

One of the most important and exam oriented question from Chapter name- Arithmetic Progression
Class 10th
Chapter number- 9
Exercise :- 9.6
This type of question has been asked in previous years exams.
In this question we have been given an arithmetic progression whose nth term is given by yn = 9 – 5n . And we have to find out sum of this progression of first 15 terms.

CBSE DHANPAT RAI publication
CBSE Mathematics Class 10th
Question 5(iv)

Share

1 Answer

  1. Given A.P. has nth term, an = 9 – 5n

    and number of terms(n) = 15

    So, an = 9 – 5(15) = -66

    On putting n = 1, we get a, first term of the A.P.,

    a = 9 – 5 = 4

    S15 = n[a + an]/2

    = 15(4 – 66)/2 = 15 x (-31) = -465

    Hence, the sum of the first 15 terms of given A.P. is -465.

    • 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