Let the principal amount lent be $PP$P. The annual compound interest rate is 124%, which can be expressed as a multiplier of $1+1.24=2.241\; +\; 1.24\; =\; 2.24$1+1.24=2.24.

The person receives three equal installments of ₹91,854. The timing of the installments is as follows:

1. First installment (at time 0): ₹91,854
2. Second installment (after 1 year): ₹91,854
3. Third installment (after 2 years): ₹91,854

Calculation of Future Value for Each Installment

1. First Installment: Since it is paid immediately, it does not earn any interest.

   $Future Value=91,854\backslash text\{Future\; Value\}\; =\; 91,854$Future Value=91,854

2. Second Installment: This installment is paid after 1 year, so it will earn interest for 1 year.

   $Future Value=91,854\times 2.24=205,181.76\backslash text\{Future\; Value\}\; =\; 91,854\; \backslash times\; 2.24\; =\; 205,181.76$Future Value=91,854×2.24=205,181.76

3. Third Installment: This installment is paid after 2 years, so it will earn interest for 2 years.

   $Future Value=91,854\times (2.24{)}^2=91,854\times 5.0176\approx 460,354.57\backslash text\{Future\; Value\}\; =\; 91,854\; \backslash times\; (2.24)^2\; =\; 91,854\; \backslash times\; 5.0176\; \backslash approx\; 460,354.57$Future Value=91,854×(2.24)2=91,854×5.0176≈460,354.57

Total Amount Received

Now, we sum the future values of all installments:

$Total Amount Received=91,854+205,181.76+460,354.57\approx 757,390.33\backslash text\{Total\; Amount\; Received\}\; =\; 91,854\; +\; 205,181.76\; +\; 460,354.57\; \backslash approx\; 757,390.33$Total Amount Received=91,854+205,181.76+460,354.57≈757,390.33

Calculation of Principal Amount

The total amount received can be equated to the amount owed after 2 years. The formula is:

$P\times (2.24{)}^2=757,390.33P\; \backslash times\; (2.24)^2\; =\; 757,390.33$P×(2.24)2=757,390.33

Calculating $PP$P:

$P\times 5.0176=757,390.33\hspace{0.25em} ⟹\hspace{0.25em} P=\frac{757,390.33}{5.0176}\approx 150,000P\; \backslash times\; 5.0176\; =\; 757,390.33\; \backslash implies\; P\; =\; \backslash frac\{757,390.33\}\{5.0176\}\; \backslash approx\; 150,000$P×5.0176=757,390.33⟹P=5.0176757,390.33​≈150,000

Total Interest Earned

The total interest earned by the person is:

$Interest=Total Amount Received-Principal=757,390.33-150,000\approx 607,390.33\backslash text\{Interest\}\; =\; \backslash text\{Total\; Amount\; Received\}\; –\; \backslash text\{Principal\}\; =\; 757,390.33\; –\; 150,000\; \backslash approx\; 607,390.33$Interest=Total Amount Received−Principal=757,390.33−150,000≈607,390.33

Thus, the amount of interest earned by him is approximately ₹607,390.33.