Question 8 (OR 2 nd question)
If 7 times the 7 th term of an A.P is equal to 11 times its 11 th term, then find its 18th term.

CBSE Class 10 Sample Paper for 2019 Boards
CBSE Class 10 Sample Paper for 2019 Boards
Last updated at Dec. 16, 2024 by Teachoo
Question 8 (OR 2 nd question)
If 7 times the 7 th term of an A.P is equal to 11 times its 11 th term, then find its 18th term.
Question 8 (OR 2nd question) If 7 times the 7th term of an A.P is equal to 11 times its 11th term, then find its 18th term. We know that an = a + (n – 1)d Given that 7 times the 7th term is equal to 11 times its 11th term 7 × a7 = 11 × a11 7 × (a + (7 – 1)d) = 11 × (a + (11 – 1)d) 7 × (a + 6d) = 11 × (a + 10d) 7a + 42d = 11a + 110d 7a – 11a = 110d – 42d –4a = 68d a = 68𝑑/(−4) a = –17d Now, we need to find the 18th term a18 = a + (18 – 1)d = a + 17d Putting a = –17d = –17d + 17d = 0 So, 18th term is 0