Question

Fill in the blank in the following table, given that a is the first term, d the common difference, and a_n nth term of the AP:

a	d	n	an
-18.9	2.5	______	3.6

Answer 1

a	d	n	an
-18.9	2.5	10	3.6

Explanation:

a = -18.9, d = 2.5, a_n = 3.6, n = ?

We know that,

a_n = a + (n - 1) d

3.6 = -18.9 + (n - 1) 2.5

3.6 + 18.9 = (n - 1) 2.5

22.5 = (n - 1) 2.5

`("n" - 1) = (22.5)/2.5`

n - 1 = 9

n = 10

Hence, n = 10