Question

Which term of the sequence $72,70,68,66,.......$ is $40$?

Answer 1

Given,

$a=72$

$d=-2$

$a_n=40$

$n=?$

solution:

$a_n=a+(n-1)d$

$40=72+(n-1)(-2)$

$-32=-2n+2$

$-34=-2n$

$n=17.$

So, the $17$th term of the sequence is $40$.