Looks like AI can solve this type problem. Give AI a few years and it'll be
able to solve any mathematics problem. In the beginning, anybody could beat
AI in chess. But the last time a human could beat AI in chess was in 2008.
It hasn't quite gotten there in mathematics. But give it time and it will!
[In the US, we use a DOT "." for a decimal point, and COMMAS "," to separate
digits in groups of three. It is just the opposite in your country. But nobody
separates digits in groups of three when calculating.]
Since the bulldozer drops in value by 20% each year means that each year, its
value is only 80% of what it was the year before. So, we are talking about the
geometric sequence with first term a1=160,000, and common ratio
r=0.80, and its nth term is an = vn.
(a)
160,000, (0.80)(160000), (0.80)2(160000), (0.80)3(140000),...
(b)
Since it will only take a few years, it's easier to do it this way
The 1st year the value is $160,000.
The 2nd year the value is $160,000(0.80) = $128,000.
The 3rd year the value is $128,000(0.08) = $102,400.
The 4th year the value is $102,000(0.80) = $81,920.
So the 4th year is the first year its value will be less than $100,000 all year.
But your teacher might expect you to use the formula. So you'd do it
this way to please your teacher:
So the year after 3.10628372 years its value will be less than $100,000.
That means that the 4th year is the first year its value will be less
than $100,000 all year.
Edwin