Question

A page from the Saving Bank Account of Mr. Prateek is given below:

Date	Particulars	Withdrawal (In Rs.)	Deposit (In Rs.)	Balances (In Rs.)
Jan $1^{st}$ $2006$	B/F	-	-	$1,270$
Jan. $7^{th}$ $2006$	By Cheque	-	$2,310$	$3,580$
March $9^{th}$ $2006$	To Self	$2,000$	-	$1,580$
March ${26}^{th}$ $2006$	By Cash	-	$6,200$	$7,780$
June ${10}^{th}$ $2006$	To Cheque	$4,500$	-	$3,280$
July ${15}^{th}$ $2006$	By Clearing	-	$2,630$	$5,910$
October ${18}^{th}$ $2006$	To Cheque	$530$	-	$5,380$
October ${27}^{th}$ $2006$	To Self	$2,690$	-	$2,690$
November $3^{rd}$ $2006$	By cash	-	$1,500$	$4,190$
December $6^{th}$ $2006$	To Cheque	$950$	-	$3,240$
December ${23}^{rd}$ $2006$	By Transfer	-	$2,920$	$6,160$

If he receives Rs. $198$ as interest on $1^{st}$ January, $2007$, find the rate of interest paid by the bank.

Answer 1

Month	Minimum balance between ${10}^{th}$ day and last day (in Rs.)	Qualifying amount for interest (in Rs.)
January	$3580$	$3580\times 2=7160$
February	$3580$
March	$1580$	$1580$
April	$7780$	$7780\times 2=15560$
May	$7780$
June	$3280$	$3280\times 2=6560$
September	$5910$
October	$2690$	$2690$
November	$4190$	$4190$
December	$3240$	$3240$
Total		Rs. $52800$

$\therefore$ Principle for $1$ month $($i.e. $\frac{1}{12}$ year$)=$ Rs. $52800$.

Interset recived $=$ Rs. $198$

$\therefore$ Rate of interest $=\frac{198\times 100}{52800\times \frac{1}{12}}\%$ $($Rate of interest $=\frac{S.I.\times 100}{P\times T}\%)$

$=\frac{198\times 100}{4400}\%=\frac{198}{44}\%$

$=\frac{9}{2}\%=4.5\%$ p.a