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Question

Vipul and Manish invested the sum of Rs. 15000 and Rs. 20000 at the rate of 20 percent p.a and 30 percent p.a. respectively on compound interest (compounding annually). If time period is 3 years for both, then what will be the total compound interest earned by Vipul and Manish ?

This question was previously asked in
SSC CGL 2020 (Tier-2) Statistics Previous Year Paper 3 (28-Jan-2022)
The correct answer is

Rs. 34860

Calculating Total Compound Interest for Multiple Investments

This problem involves calculating the compound interest earned by two different individuals, Vipul and Manish, on their respective investments over a period of 3 years. We need to find the compound interest for each person and then sum them up to get the total compound interest.

The formula for the Amount (A) under compound interest is given by:

\( A = P \left(1 + \frac{R}{100}\right)^T \)

Where:

  • \( P \) is the Principal amount
  • \( R \) is the Rate of interest per annum
  • \( T \) is the Time period in years

The Compound Interest (CI) is then calculated as:

\( CI = A - P \)

Let's calculate the compound interest for Vipul and Manish separately.

Compound Interest Calculation for Vipul

Vipul's investment details:

  • Principal (P) = Rs. 15000
  • Rate (R) = 20% p.a.
  • Time (T) = 3 years

Using the formula for the Amount:

\( A_{Vipul} = 15000 \left(1 + \frac{20}{100}\right)^3 \)

\( A_{Vipul} = 15000 \left(1 + 0.2\right)^3 \)

\( A_{Vipul} = 15000 \left(1.2\right)^3 \)

\( A_{Vipul} = 15000 \times 1.728 \)

\( A_{Vipul} = 25920 \)

Now, calculating the Compound Interest for Vipul:

\( CI_{Vipul} = A_{Vipul} - P_{Vipul} \)

\( CI_{Vipul} = 25920 - 15000 \)

\( CI_{Vipul} = 10920 \)

So, Vipul earned a compound interest of Rs. 10920.

Compound Interest Calculation for Manish

Manish's investment details:

  • Principal (P) = Rs. 20000
  • Rate (R) = 30% p.a.
  • Time (T) = 3 years

Using the formula for the Amount:

\( A_{Manish} = 20000 \left(1 + \frac{30}{100}\right)^3 \)

\( A_{Manish} = 20000 \left(1 + 0.3\right)^3 \)

\( A_{Manish} = 20000 \left(1.3\right)^3 \)

\( A_{Manish} = 20000 \times 2.197 \)

\( A_{Manish} = 43940 \)

Now, calculating the Compound Interest for Manish:

\( CI_{Manish} = A_{Manish} - P_{Manish} \)

\( CI_{Manish} = 43940 - 20000 \)

\( CI_{Manish} = 23940 \)

So, Manish earned a compound interest of Rs. 23940.

Total Compound Interest Earned

The total compound interest earned by Vipul and Manish is the sum of their individual compound interests:

\( \text{Total CI} = CI_{Vipul} + CI_{Manish} \)

\( \text{Total CI} = 10920 + 23940 \)

\( \text{Total CI} = 34860 \)

The total compound interest earned by Vipul and Manish is Rs. 34860.

Investor Principal (P) Rate (R) Time (T) Amount (A) Compound Interest (CI)
Vipul Rs. 15000 20% 3 years Rs. 25920 Rs. 10920
Manish Rs. 20000 30% 3 years Rs. 43940 Rs. 23940

Total Compound Interest = \( CI_{Vipul} + CI_{Manish} = 10920 + 23940 = 34860 \)

Thus, the total compound interest earned is Rs. 34860.

Revision Table: Compound Interest Concepts

Term Definition Formula Snippet
Principal (P) The initial amount invested or borrowed. \( P \)
Rate (R) The percentage at which interest is calculated per period. \( R\% \)
Time (T) The duration for which the money is invested or borrowed. \( T \) years
Amount (A) The total sum including principal and interest after a certain time. \( A = P(1 + R/100)^T \)
Compound Interest (CI) Interest calculated on the principal and the accumulated interest from previous periods. \( CI = A - P \)

Additional Information: Compounding Frequency

In this problem, the interest is compounded annually. Compound interest can also be calculated with different frequencies, such as semi-annually, quarterly, monthly, or even daily. When interest is compounded more frequently than annually, the formula is slightly adjusted:

\( A = P \left(1 + \frac{R}{100n}\right)^{nT} \)

Where:

  • \( n \) is the number of times interest is compounded per year.
  • For semi-annual compounding, \( n=2 \).
  • For quarterly compounding, \( n=4 \).
  • For monthly compounding, \( n=12 \).

A higher compounding frequency generally leads to a higher amount of compound interest earned over the same time period and interest rate, because interest starts earning interest sooner.

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Similar Questions

  1. If interest be compounded half-yearly, then find the compound interest on ₹8,000 at the rate of 20% per annum for 1 year.

  2. What is the compound interest on a sum of ₹25,000 after three years at a rate of 12 per cent per annum interest compounded yearly?

  3. Find the amount (integral value only) if a sum of ₹6,500 is being borrowed at 10% interest per annum for 2 years if interest is compounded half-yearly

  4. A sum invested at compound interest amounts to Rs. 7,800 in 3 years and Rs. 11,232 in 5 years. What is the rate per cent?

  5. What is the amount (in ₹) of a sum of ₹32,000 at 20% per annum for 9 months, compounded quarterly?

  6. The compound interest on a certain sum of money at 21% p.a. for 2 years is Rs. 11,138.40 (interest compounded yearly). The total amount received (in Rs) after 2 years is:

  7. Divide Rs. 66,300 between A and B in such a way that the amount that A receives after 8 years is equal to the amount that B receives after 10 years; with compound interest being compounded annually at a rate of 10% per annum.

  8. What is the compound interest (in Rs.) on a sum of Rs. 8192 for \(1 \frac{1}{4}\)  years at 15% per annum, if interest is compounded 5-monthly ?

  9. A sum of Rs. 3125 amounts to Rs. 3515.20 in 3 years at x% p.a., interest being compounded yearly. What will be the simple interest (in Rs.) on the same sum and for the same time at (x + 2)% p.a.?

  10. The interest (in Rs.) to be paid on a sum of Rs. 30000 at 15% p,a. after \(2\frac{2}{3}\)  years if interest compounded yearly, is:


Important Questions from Compound Interest

  1. The certain sum amounts to Rs. 9,982.50 in \(2\frac{1}{2}\)  years at 12% p.a., interest compounded 10-monthly. The sum (in Rs.) is:

  2. The difference between the simple interest and the compound interest compounded annually on a certain sum of money for 2 years at a rate of 8% per annum is Rs. 16.80. Find the principle amount. 

  3. If a sum of ₹ 2000 is lent at 10% p.a. compound interest, what is the interest for the second year?

  4. A sum becomes 5 times of itself in 3 years. at compound interest (interest is compounded annually). In how many years. will the sum becomes 125 times of itself?

  5. If the compound interest on a certain sum of money for two years at 9% p.a. is Rs. 3,762, then the sum is:

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