A compnay paid 140000 for a new 18wheeler When it is 10years

A compnay paid $140,000 for a new 18-wheeler. When it is 10-years old it will be worth $30,000. Using a straight-line depreciation, the value of the truck in dollars, V, is the linear function of it\'s age in years, n. Find the function and the value when the truck is 5 years old.

Write the value of the truck V as a function of it\'s age in years, n.

What is the value of the truck when it is 5 years old?

Solution

At n = 0, V = 140000
at n = 10, V = 30,000
Use:
(V-V1)/(n-n1) = (V2-V1)/(n2-n1)
(V-140000)/(n-0) = (30000 - 140000)/(10-0)
(V-140000)/n = -110000/10
V-140000 = -11000 n
V = 140000 - 11000 n
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put n=5
V = 140000 - 11000*5
= $85000
Answer: $85000