Question

The first term of an A.p is 3 and the fifth term is 9 find the number of terms in the progression if the last is 81

Answer 1

Answer:

53rd Term

Step-by-step explanation:

First term, a = 3

Fifth term = 9

nth term = 81

the nth term can be calculated using the formula

${t}^{n} = a + (n - 1) \times d$

$9 = 3 + (5 - 1) \times d$

$4d = 9 - 3$

$d = \frac{6}{4} = 1.5$

Now when nth term = 81

$81 = 3 + (n - 1) \times 1.5$

$(n - 1) \times 1.5 = 81 - 3$

$1.5n - 1.5 = 78$

$1.5n = 78 + 1.5$

$n = \frac{79.5}{1.5} = 53$