Q. You can afford a $250 per month car payment. Youve found a 3 year loan at 5% interest. How big of a loan can you afford?
Loan Calculation Overview: First, we need to understand that the loan will be paid off in monthly installments over 3 years, which is 36 months. We also know that the monthly payment is $250 and the annual interest rate is 5%. To find the maximum loan amount, we will use the formula for an installment loan which takes into account the interest rate.
Monthly Payment Formula: The formula for the monthly payment M for a loan with principal amount P, monthly interest rate r, and number of payments n is:M=P×(1+r)n−1r(1+r)nWe need to rearrange this formula to solve for P, the principal amount, which is the maximum loan amount we can afford.
Convert Annual to Monthly Rate: First, we convert the annual interest rate to a monthly interest rate by dividing by 12, since there are 12 months in a year.Monthly interest rate r = Annual interest rate / 12r=125%r=120.05r=0.0041666667
Calculate Number of Payments: Next, we calculate the number of payments n, which is the number of months in 3 years.n=3 years×12 months/yearn=36 months
Solve for Principal Amount: Now we can rearrange the formula to solve for P:P=r(1+r)nM×[(1+r)n−1]We will plug in the values for M, r, and n to find P.
Substitute Values into Formula: Substitute the values into the rearranged formula:P=[0.0041666667(1+0.0041666667)36]250×[(1+0.0041666667)36−1]Now we need to calculate the values inside the brackets and then divide 250 by that result to find P.
Calculate (1+r)n: First, calculate (1+r)n:(1+0.0041666667)36This requires using a calculator to raise (1+0.0041666667) to the power of 36.
Calculate Denominator: After calculating the above expression, we get: (1+0.0041666667)36≈1.1940523
Divide Monthly Payment: Now we calculate the entire denominator of the formula:1.1940523−10.0041666667×1.1940523This simplifies to:0.19405230.0049753
Find Maximum Loan Amount: After calculating the denominator, we get: 0.19405230.0049753≈0.025636
Find Maximum Loan Amount: After calculating the denominator, we get:0.0049753/0.1940523≈0.025636Finally, we divide the monthly payment by this result to find the principal amount (P):P=0.025636250
Find Maximum Loan Amount: After calculating the denominator, we get:0.0049753/0.1940523≈0.025636Finally, we divide the monthly payment by this result to find the principal amount (P):P=0.025636250After performing the division, we find the maximum loan amount (P) that can be afforded:P≈9753.47