Question

Which term of the sequence $4,9,14,19,....$ is $124$?

Answer 1

Clearly, the given sequence is an A.P. with first term $a(=4)$ and common difference $d(=5)$

Let $124$ be the term of the given sequence. Then,

$a_n=124$

$⟹a+(n+1)d=124$

$⟹4+(n-1)\times 5=124$

$⟹5n-1=124$

$⟹5n=125$

$⟹n=25$

Hence, ${25}^{th}$ term of the given sequence is $124$.