Question

Find the number of terms in the sequence $4,12,20,...,108.$

Answer 1

From the given sequence, we can derive that

$a=4,d=8$, $a_n=108$

We know the formula for $n^{th}$ term of an AP i.e.,

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

$108=4+(n-1)8$

$108=4+8n-8$

$108=8n-4$

$8n=108+4$

$8n=112$
So, $n=14$