Question

Rs. 400 is simple interest for a sum for 4 years at 10% rate of interest per annum. Find the compound interest for the same sum at same rate of interest for same time period​

Answer 1

Answer:

soln,

time (t) = 4yrs

rate(R) = 10%

Now

SI = PTR/100

or, 400= P.4.10/100

or, P = 40000/40

so, P = 4000

We know

CI = P[(1+R/100)^t-1]

= 4000[(1+10/100)^4-1]

= RS. 1856.4

Answer 2

The compound interest =  464.1 Rs

Given:

Rs. 400 is simple interest for a sum for 4 years at 10% rate of interest per annum

To find:

Find the compound interest for the same sum at same rate of interest for same time period​

Solution:

Let P be the sum of amount

Given Rate of interest R = 10% and Time period T = 4 years

As we know Simple interest I = PTR/100

⇒ From above data, I = P(4)(10)/100

= P(4)/10 = 2P/5

Given that Simple interest for sum = 400

⇒ 2P/5 = 400

⇒ 2P = 2000

⇒ P = 1000

The sum of amount is 1000

Now find the Compound interest for P = 1000, at R = 10% per annum for Time period T = 4 years

As we know  

Compound interest (C.I)  = P[(1+R/100)^t -1 ]

⇒ 1000 [ (1+10/100)⁴ -1]

⇒ 1000 [ (1 + 1/10)⁴ - 1 ]

⇒ 1000 [ (1 + 0.1)⁴ - 1 ]

⇒ 1000 [ (1.1)⁴ - 1 ]

⇒ 1000 [ 1.4641 - 1 ]

⇒ 1000 [ 0.4641 ]

⇒ 464.1

The compound interest =  464.1 Rs

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