Question

A certain sum of money at compound interest becomes rupees 7296 in 2 years and Rs 7950 and 70 Paisa in 3 years find the rate of interest

Answer 1

i think there should be 7396 in place of 7296 so that it rate will be 7.5% for sum of 6400
.


here we have to find rate so sum does not matter.

2 years amount is sum for 3rd year

$p(1 + \frac{r}{100} ) = amount \\ or \: 7296(1 + \frac{r}{100} ) = 7950.7 \\ or \: 1 + \frac{r}{100} = \frac{7950.7}{7296 } \\ r = \frac{7950.7 - 7296}{7296} \times 100 \\ r = \frac{654.7}{7296} \times 100 \\ r = 8.97\%$
so Rate is 8.97%.
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in case of 7396

R= (554.7/7396 ) ×100

R= 7.5%

Answer 2

Answer:

Step-by-step explanation:

Compound interest formula:$Amount=P{(1+\frac{r}{100})}^n$

$when n=3,\\7950.70=P{(1+\frac{r}{100})}^3.....(1)$

$when n=2,\\7296=P{(1+\frac{r}{100})}^2......(2)$

Now divide (2) by(1)

$\frac{795070}{729600}=(1+\frac{r}{100})$

$\frac{79507*100}{72960}=100+r$

$108.97=100+r\\r=8.97%$