Question

At what rate percent will a. Sum of rs 640 be compounded to rs 774.40 in two years

Answer 1

Principal (P) = Rs. 640
Amount (A) = Rs. 774.40
Time (n) = 2 years
Rate of interest (R) % = ?

We know that,

$A = P {(1 + \frac{R}{100} )}^{n} \\ \\ 774.40 = 640 {(1 + \frac{R}{100} )}^{2} \\ \\ 774.40 = 640 {(1 + \frac{R}{100} )}^{2} \\ \\ \frac{774.40}{640} = {(1 + \frac{R}{100} )}^{2} \\ \\ \frac{77440}{640 \times 100} = {(1 + \frac{R}{100} )}^{2} \\ \\ \frac{121}{100} = {(1 + \frac{R}{100} )}^{2} \\ \\ { (\frac{11}{10}) }^{2} = {(1 + \frac{R}{100} )}^{2} \\ \\ \frac{11}{10} = 1 + \frac{r}{100} \\ \\ \frac{11}{10} - 1 = \frac{R}{100 } \\ \\ \frac{11 - 10}{10} = \frac{r}{100} \\ \\ \frac{1}{10 } = \frac{R}{100} \\ \\ \frac{1}{10} \times 100 = r \\ \\ 10 = R$

Hence, Rate of interest (R) % = 10%

Answer 2

Answer:

Step-by-step explanation:

A=p(1+r/100)^2

774.40=640(1+r/100)^2

774.40/640=(1+r/100)^2

121/100=(1+r/100)^2

(121/100)^2=1+r/100

11/10=1+r/100

11/10-1=r/100

11-10/10=r/100

1/10=r/100

R=1/10×100

R=10%