
Michael C. answered 03/05/17
Tutor
4.9
(10)
Patient and Qualified Math Tutor
This is an economics problem
First, with a down payment of $40,000, what remains to be paid is 125000-40000=$85,000 over a 25 year period with an apr of 25%
hence we have to calculate the monthly payment at a monthly rate of 7.5/12 % = 0.625% or 5/8%
Method 1
Use the equation for capital recovery factor CRF = i(1+i)n/((1+i)n - 1)
putting i = 0.625% = 0.00625, and n = 300 months, the CRF = 0.0074
Hence monthly payment = 85,000 * 0.0074 = $628 per month
Method 2
you can go online (google.com) and find annuity tables; there are about 8 columns, the column you are interested in is capital recovery factor or Annuity given Principal or A/P
You will have to do a bit of interpolation as 5/8 does not appear in the table but 1/2 and 3/4 appear, hence 5/8 would be midway between the two. Also in 25 years = 25*12 = 300 months; in the tables 240, and 360 occurs, 300 happens to be the midpoint, from that interpolation (A/P, 5/8, 300) = 0.0075
Hence the monthly payment is, $85,000 * 0.0075 = $638 per month (which is close to the value from method 1).