Question

The compound interest on a certain sum for 2 years at 10% per annum is rs. 420. The simple interest on the same sum for double the time at half the rate percent per annum is:

Answer 1

hello....

let X is the principal,

X* 110/100 X 110/100 = X + 420

1.21 X = X + 420

1.21X - X = 420

.21 X= 420

X = 420/ .21 = 2000

Now S I, for 2 years,

X * 2* 10/100 = 4000


thank you ☺

Answer 2

Answer:

rs.400

Step-by-step explanation:

Let the principal be x

Compound interest = 420

Amount = Principal +Interest = x+420

Time = 2 years

rate = 10%

$A=P(1+r)^t$

$x+420=x(1+0.1)^2$

$x+420=1.21x$

$420=0.21x$

$\frac{420}{0.21}=x$

$2000=x$

Principal = 2000

We are supposed to find the simple interest on the same sum for double the time at half the rate percent per annum

Time = 4 years

Rate = 5%

$SI =\frac{P \times R \times T}{100}$

$SI =\frac{2000 \times 5 \times 4}{100}$

$SI =400$

Hence the simple interest is rs.400