Question

at what rate percent per annum will a sum of rupees 4000 rupees 1324 as compound interest in 3 years

Answer 1

Putting the values in the formula
CI= P(1+r/100)^n-P

we get
1324 = 4000[(1+r/100)^3-1]
on solving we get
1324/4000+1=(1-r/100)^3
5324/4000=(1-r/100)^3
1331/1000=(1-r/100)^3
(11/10)^3=(1-r/100)^3
on cancelling cube from both sides we get
11/10=1-r/100
on solving we get
r=10%

Answer 2

Answer: 10%

Step-by-step explanation:

Sol:

Given that principal = Rs.4000

And C I = Rs.1324

Amount = Principal + C.I

A =  4000 + 1324 .

A = Rs. 5324 let the rate of interest = r%. Given time = 3 years.

A = p×(1 + r/100)n

5324 = 4000(1 + r/100)3

5324/4000 = (1 + r/100)3

1331/1000 = (1 + r/100)3    [ cube root on both sides] (11 / 10)3 = (1 + r/100)3

11 / 10 = 1 + r / 100

11 / 10-1 = r / 100.

1 / 10 = r / 100

r = 100/10

∴ r =10%.

Hence the rate of interest is 10%.