Question

on what date will Rs.1,950 lent on 5th January, 2011 amount to Rs. 2,125.50 at 5 per cent per annum simple interest ?
if the interest on Rs. 2,400 be more than the interest on Rs. 2,000 by Rs.60 in 3 years at the same rate per cent; find the rate.

Answer 1

Date = 5th Jan, 2011

P = 1950

A = 2125.50

R = 5  

I = A-p = 175.5

$I=\frac{P T R}{100}$

$175.5=1950 \times T \times \frac{5}{100}$

$T=\frac{351}{195}$

$T=\frac{351}{195} \times 365$

$T=73 \times 9=657 Days$    

657 Days = 1 year 292

5th Jan, 2011 to 1 year = 5th jan, 2012

292- near to one year. Less than 73 days. Calculate from December.

Dec = 31, Nov = 30, Oct = 12 Days which means 19th Oct , 2012 we will get interest.

$P_{1}=2000$

$T_{1}=3\ years$

$R_{1}=r$

$I_{1}=\frac{P_{1} T_{1} R_{1}}{100}$

$=\frac{(2000 \times 3 \times r)}{100}$

$P_{2}=2400$

$T_{2}=3\ years$

$R_{2}=r$

$I_{2}=\frac{P_{2} T_{2} R_{2}}{100}$

$=2400 \times 3 \times \frac{r}{100}$

And as given $I_{2}=I_{1}+60$

$\frac{I_{1}}{I_{2}}=\frac{2000 \times 3 \times r}{2400 \times 3 \times r}$

$\frac{I_{1}}{I_{1}+60}=\frac{5}{6}$

$6 I_{1}=5\left(I_{1}+60\right)$

$I_{1}=300$

Substitute $I_{1}$ in the above  

$300=\frac{2000 \times 3 \times R}{100} \Rightarrow R=5$

Rate percent is 5 per annum.

Answer 2

on what date will Rs.1,950 lent on 5th January, 2011 amount to Rs. 2,125.50 at 5 per cent per annum simple interest ?

if the interest on Rs. 2,400 be more than the interest on Rs. 2,000 by Rs.60 in 3 years at the same rate per cent; find the rate