Compound Interest Ques 11
Question
The compound interest (compounded annually) on Rs. 9300 for 2 years at the rate of $ R \%$ p.a. is Rs. 4092. Had the rate of interest been ( $R-10) \%$, what would have been the interest on the same sum of money for the same time? (2 years)
(1) Rs. 1945
(2) Rs. 2046
(3) Rs. 1974
(4) Rs. 2027
(5) Rs. 1953
(Indian Bank PO (Pre.) Exam, 21.01.2017 (2nd Sitting))
Show Answer
Answer: (5)
Solution: (5)
Amount $=$ Rs. $(9300+4092)$ $=$ Rs. 13392
$\therefore A=P(1+\frac{R}{100})^{T}$
$\Rightarrow 13392=9300(1+\frac{R}{100})^{2}$
$\Rightarrow \frac{13392}{9300}=(1+\frac{R}{100})^{2}$
$ \Rightarrow \frac{144}{100}=(\frac{12}{10})^{2}=(1+\frac{R}{100})^{2} $
$ \Rightarrow 1+\frac{R}{100}=\frac{12}{10}$
$ \Rightarrow \frac{R}{100}=\frac{12}{10}-1=\frac{2}{10}$
$ \Rightarrow R=\frac{2}{10} \times 100=20 \% \text { p.a. }$
New rate $=(R-10) \%=10 \%$
$\therefore $ C.I. $=P[(1+\frac{R}{100})^{T}-1]$
$ =9300[(1+\frac{10}{100})^{2}-1] $
$ =9300[(\frac{11}{10})^{2}-1] $
$ =9300(\frac{121}{100}-1) $
$=\frac{9300 \times 21}{100}=\text { Rs. } 1953$
BETA
