Arithmetic Sequences

[discreditedvalidity]

Here is the problem:

The purchase value of an office computer is $12,500. Its annual depreciation is $1875. Find the value of the computer after 6 years.

It sounds easy, and I plugged it into this formula

A(6) = 12,500 + (6-1)-1875
=12,500 + (5)-1875
=12,500 + (-9375)
= $3175


The answer is $1250 though, and when I do it by subtracting 1875 six times, I get the right answer. But the teacher wants us to use the formula. What am I doing wrong? Thanks.

 

[Gene]

It is worth 25,000 in year zero, not year 1 so it is
12500-(6-0)(1875). Think about after 1 year with the formula as you used it.

 

[daon]

Cost = 12500
Worth lost per year = 1875
Years passed = 6

Total worth after 6 years = 12500 - 6*1875 = 1250

 

[discreditedvalidity]

Ohhhh, I understand, thank you.