Question

Jasleen saved $Rs.5$ in the first week of the year and then increased her weekly savings by $Rs.1.75$ each week. In what week will her weekly savings be $Rs.20.75$?

Answer 1

Suppose Jasleen's weekly savings will be $Rs.20.75$ in the $n^{th}$ week.

Clearly, Jasleen's weekly savings from an A.P. with first term $a=5$ and common difference $d=1.75$.
$\therefore n^{th}$ term $20.75$

$⟹a+(n-1)d=20.75$

$⟹5+(n-1)\times 1.75=20.75$

$⟹(n-1)\times 1.75=15.75$
$⟹n-1=\frac{15.75}{1.75}⟹n-1=9⟹n=10$
Hence, Jasleen's weekly savings will be $Rs.20.75$ in ${10}^{th}$ week.