Question

If 7 times the seventh term of an A.P. is equal to 11 times its eleventh term, the value of eighteenth term of the A.P. is___

Answer 1

Seventh term of the AP = a + 6d

Eleventh term of the AP = a + 10d

7(a + 6d) = 11(a + 10d)

$\to$ 7a + 42d = 11a + 110d

$\to$ 4a + 68d = 0

$\to$ a + 17 d = 0

So, the eighteenth term is zero.