Question

A theatre has 50 seats on the front row. There are 4 additional seats in each following row.

Answer 1

$\boxed { \boxed { T_n = a_1 + d(n - 1)}}$

$\text {Given that }a_1 = 50 \text { and } d = 4$

$T_n = 50 + 4(n - 1)$

$T_n = 50 + 4n - 4$

$T_n = 46 + 4n$

$\boxed { \boxed {T_n = 46 + 4n }}$

When n = 20,
$T_{20} = 46 + 4(20) = 126$

$\boxed { \boxed {\text{Answer: The 20th term is 126}}}$