Question

the first and last term of an ap are 4 and 81 respectively. if the common difference is 7. how many terms are there in ap??.plzzz answer it fast.its urgent..plzz help me out

Answer 1

First term, a = 4
Common difference, d = 7
Let the number of terms be n
Then, Tn = 81
$a + (n - 1)d = 81 \\ n = \frac{81 - 4}{7} + 1 = 12$