This is an Arithmetic sequence.
An arithmetic sequence is shown as:
[tex]a_1,a_2,a_3,...,a_n[/tex]
and
[tex]a_2-a_1=a_3-a_2=...=a_n-a_{n-1}=d[/tex]
We don't know [tex]a_n[/tex] which is the last term and it is computed by:
[tex]a_n=a_1+d(n-1)[/tex]
Our [tex]a_1[/tex] is the amount Sally had on August 1 which is equal to 3.00
We compute for [tex]a_n [/tex] which is also [tex]a_{31}[/tex]. The common difference in the problem is 0.25.
[tex]a_{31}=3.00+0.25(31-1)=3.00+0.25(30)=3.00+7.50=10.50[/tex]
Therefore she would have P10.50 by the end of August.
