Question

(i) At what rate per cent per annum will Rs. 630 produce an interest of Rs. 126 in 4 years?
(ii) At what rate per cent per year will a sum double itself in $6\frac{1}{4}$ years?

Answer 1

(i) P= Rs. 630, I=Rs. 126, T= 4 years
$R=\frac{100\times 1}{P\times T}=\frac{100\times 126}{630\times 24}=\frac{100}{20}=$ 5%
(ii)Let P=Rs. 100
$\therefore$ Amount = $2\times Rs.100=Rs.200$
Interest =A-P
=Rs. 200-Rs.100=Rs.100
$T=6\frac{1}{4}years=\frac{25}{4}$ years
$R=\frac{100\times I}{P\times T}=\frac{100\times 100}{100\times \frac{25}{4}}$ % = $\frac{100\times 100}{100}\times \frac{4}{25}=16$