Using an arithmetic sequence, it is found that:
i) They collected 300 bottles on June 25th.
ii) The day was July 18th.
What is an arithmetic sequence?
In an arithmetic sequence, the difference between consecutive terms is always the same, called common difference d.
The nth term of an arithmetic sequence is given by:
[tex]a_n = a_1 + (n - 1)d[/tex]
In which [tex]a_1[/tex] is the first term.
In this problem, the sequence is: {417 ,404 ,391, .........}, hence the first term is [tex]a_1 = 417[/tex], the common difference is d = -13, and the equation is:
[tex]a_n = 417 - 13(n - 1)[/tex]
Item i)
They started on June 15th, hence June 25th is the 10th day, thus:
[tex]a_{10} = 417 - 13(9) = 300[/tex]
They collected 300 bottles on June 25th.
Item ii)
This is n days after June 15th, for which [tex]a_n = 1[/tex], hence:
[tex]a_n = 417 - 13(n - 1)[/tex]
[tex]1 = 430 - 13n[/tex]
[tex]13n = 429[/tex]
[tex]n = 33[/tex]
33 days after June 15th is July 18th.
More can be learned about arithmetic sequences at https://brainly.com/question/6561461