Ramkali saved Rs. 5 in the first week of a year and then increased her weekly savings by Rs. 1.75. If in the nth week,

Solution:

$\mathrm{t}_{1}=$ Rs. 5 (savings in the lst week)

$t_{2}=R s .5+R s .1 .75=R s .6 .75$

(savings in the 2 nd week)

$t_{3}=$ Rs. $6.75+$ Rs. $1.75=$ Rs. $8.50$

(savings in the $3 \mathrm{rd}$ week)

......................

$\mathrm{t}_{\mathrm{n}}=$ Rs. $20.75$

$\Rightarrow a+(n-1) d=20.75$

$\Rightarrow 5+(n-1) \times 1.75=20.75$

$\Rightarrow(\mathrm{n}-1) \times 1.75=15.75$

$\Rightarrow \mathrm{n}-1=\frac{15.75}{1.75}=\frac{1575}{175}=9 \Rightarrow \mathrm{n}=10$

Hence, in the 10th week. Ramkali's savings will be Rs. $20.75$