Answer:
37.12 mo
Explanation:
Your total payment (P) starts at zero and increases by $774 each month. Thus, the formula for your total payment is
P = 774t
where t is the number of months.
The value (V) of your car starts at $38 713 and decreases to zero over 12 yr (144 mo) .
The monthy rate of depreciation is $38 713/144 mo = $268.84/mo.
So, the equation for the value of your car is
V = 38 713 – 268.84t
The value of your car will equal your total payments when
P = V Substitute the expressions for P and V
774t = 38 713 – 268.84t Add 268.84t to each side
1042.84t = 38 713 Divide each side by 1042.84t
t = 37.12 mo
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You can see what’s happening in a graph of the two functions.
The blue line represents the depreciating value of your car. It starts at
$38 713 when new and decreases to $25 271 after 50 mo.
The red line represents your total payments. They start at zero and increase to $38 700 after 50 mo.
The two lines intersect at (37.12, 28 733). At that point, the value of your car equals your total payments.