A loan grows to $3740 after 1 year and $4114 after 2 years with compound interest which is computed annually. Find(a) the interest rate per annum,(b) the original loan.
Q. A loan grows to $3740 after 1 year and $4114 after 2 years with compound interest which is computed annually. Find(a) the interest rate per annum,(b) the original loan.
Establish Relationship Using Compound Interest Formula: First, let's establish the relationship between the amounts after each year and the interest rate. We can use the compound interest formula, which is A=P(1+r)n, where A is the amount of money accumulated after n years, including interest, P is the principal amount (the initial amount of money), r is the annual interest rate (decimal), and n is the number of years the money is invested or borrowed for.
Set Up Equations for Each Year: We know the loan amount after 1 year A1 is $3740, and after 2 years A2 is $4114. We can set up two equations using the compound interest formula for each year:For the end of the first year:A1=P(1+r)1For the end of the second year:A2=P(1+r)2
Express P in Terms of A1 and r: We can use the first equation to express P in terms of A1 and r:P=(1+r)A1
Substitute P into Second Equation: Now we can substitute this expression for P into the second equation to find r:A2=(1+rA1)⋅(1+r)2
Simplify Equation and Solve for r: Simplify the equation by canceling out (1+r) in the numerator and denominator:A2=A1×(1+r)
Calculate r Value: Now we can solve for r by dividing both sides by A1 and then subtracting 1: (1+r)=A1A2 r=(A1A2)−1
Express r as Percentage: Plug in the values for A1 and A2 to calculate r: r=37404114−1 r≈1.10026737967914−1 r≈0.10026737967914
Find Original Loan Amount: To express r as a percentage, we multiply by 100:r=0.10026737967914×100r≈10.03%
Calculate P Using Values for A1 and r: Now that we have the annual interest rate, we can find the original loan amount (P) using the first year's equation:P=(1+r)A1
Calculate P Using Values for A1 and r: Now that we have the annual interest rate, we can find the original loan amount (P) using the first year's equation:P=(1+r)A1Substitute the values for A1 and r (as a decimal) to calculate P:P=(1+0.10026737967914)3740P≈1.100267379679143740P≈3399.97