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What is the compound interest earned on Rs. 80,000 at 40% per annum in one year, compounded quarterly?

Solution

✅ Correct Option: 2

Given:

Principal = Rs. 80,000

Interest Rate = 40% per annum

Time Period = 1 year

Compounding = Quarterly (4 times a year)


For quarterly compounding, the year is divided into 4 equal quarters, so interest is calculated and added 4 times in 1 year.

Rate per quarter =40%4=10%= \dfrac{40\%}{4} = 10\%

Number of compounding periods =1×4=4= 1 \times 4 = 4


Using the compound interest formula A=P(1+r100)nA = P(1 + \dfrac{r}{100})^n where:

P=80,000P = 80,000

r=10%r = 10\% (rate per quarter)

n=4n = 4 (number of quarters)


A=80,000×(1+10100)4A = 80,000 \times (1 + \dfrac{10}{100})^4

A=80,000×(1.1)4A = 80,000 \times (1.1)^4

Calculating (1.1)4(1.1)^4:

(1.1)2=1.21(1.1)^2 = 1.21

(1.1)4=1.21×1.21=1.4641(1.1)^4 = 1.21 \times 1.21 = 1.4641

Therefore:

A=80,000×1.4641A = 80,000 \times 1.4641

A=1,17,128A = 1,17,128


Compound Interest == Final Amount −- Principal

CI=1,17,128−80,000CI = 1,17,128 - 80,000

CI=37,128CI = 37,128

Therefore, the compound interest earned is Rs. 37,128.

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