What is the rate of interest p.c.p.a.?

I. An amount doubles itself in 5 years on simple interest.

II. Difference between the compound interest and the simple interest earned on a certain amount in 2 years is Rs. 400.

III. Simple interest earned per annum is Rs. 2000

Interest earned in scheme M =   

P1 + 201002 - 1 = 11P25

Interest earned in scheme N =  

P x k x 2100 = Pk50

Now, from the given data,

11P25 = 2 x Pk50

k = 11

Let Rs. K invested in each scheme

Two years C.I on 20% = 20 + 20 + 20x20/100 = 44%

Two years C.I on 15% = 15 + 15 + 15x15/100 = 32.25%

Now,

(P x 44/100) - (P x 32.25/100) = 528.75

=> 11.75 P = 52875

=> P = Rs. 4500

Hence, total invested money = P + P = 4500 + 4500 = Rs. 9000.

Let 'R%' be the rate of interest

From the given data,

$$\begin{gathered} 25202400 = 1 + R10041 + R1003 \\ ⇒1 + R100 = 6360 \\ ⇒R = 5 \end{gathered}$$

Hence, the rate of interest R = 5% per annum.

Given principal amount = Rs. 8000

Time = 3yrs

Rate = 5%

C.I for 3 yrs = $$\begin{gathered} 8000 x 105100 x 105100 x 105100 - 8000 \\ = Rs. 1261 \end{gathered}$$

Now, C.I for 2 yrs = $$\begin{gathered} 8000 x 105100 x 105100 \\ = Rs. 820 \end{gathered}$$

Hence, the required difference in C.I is 1261 - 820 = Rs. 441

We know that,

$$\begin{gathered} S.I. = PTR100 \\ ⇒ P = S.I x 100T x R \\ And also, \\ C.I = P1 + R100n- 1 \end{gathered}$$

From given data, P = Rs. 8625

Now, C.I  = $$\begin{gathered} 86251+41002-1 \\ = 862526252-1 \\ = 8625676625-1 \\ = 8625 x 51625 \\ C.I = Rs. 703.80 \end{gathered}$$

We know the formula for calculating

The compound interest C = P1 + r100n - 1 where P = amount, r = rate of interest, n = time

Here P = 5000, r1 = 10, r2 = 20

Then $$\begin{gathered} C = 65001 + 101002 x 1 + 201002 - 1 \\ = 6500 x 18562500 \\ = 65 x 185625 \end{gathered}$$

C = Rs. 4826.

Compound Interest for 1 ¹⁄₂ years when interest is compounded yearly = Rs.(5304 - 5000)

Amount after 1¹⁄₂ years when interest is compounded half-yearly 


Compound Interest for 1 ¹⁄₂ years when interest is compounded half-yearly = Rs.(5306.04 - 5000)

Difference in the compound interests = (5306.04 - 5000) - (5304 - 5000)= 5306.04 - 5304 = Rs. 2.04