Question

If twice the 11^th term of an A.P. is equal to 7 times of its 21^st term, then its 25^th term is equal to.

• A. 24
• B. 120
• C. 0
• D. None of these

Answer 1

Answer: (C)

0

Answer 2

Let the first term of A.P. is a and common difference is d.

11^th term of A.P. = $a + 10 d$

21^st term of A.P. = a+ 20d

$2 ( a + 10 d ) = 7 ( a + 20 d )$⇒$2 a + 20 d = 7 a + 140 d$

$5 a + 120 d = 0$ ⇒$a + 24 d = 0$

Hence 25^th term is 0.