Question

Suresh started work in $1985$ at an annual salary of $Rs.5000$ and received an increment of $Rs.200$ each year. After how many years did his income reach $Rs.7000$?

Answer 1

It can be observed that suresh gets increment of $Rs.200$ every year
so $d=200$
Income in first year was $5000$
So, a = $5000$
After $n^{th}$his salary will be $7000$
Therefore, $a_n$ = $a+(n-1)d$
$7000$ = $5000+(n-1)\left(200\right)$
$7000-5000$ = $(n-1)\left(200\right)$
$2000$ = $200n-200$
$2000+200$ = $200n$
n= $\frac{2200}{200}$
$n=11$
Therefore , in ${11}^{th}$ year , his salary will reach Rs, $7000$