The 300th term will be the difference of the sum of the first 300 terms and the sum of first 299 terms so it follows:
[tex]\begin{gathered} S_{300}=\frac{1}{2}(300)-25=125 \\ S_{299}=\frac{1}{2}(299)-25=124.5 \end{gathered}[/tex]
Therefore the 300th term is given by:
[tex]T_{300}=S_{300}-S_{299}=125-124.5=0.5[/tex]
Hence the 300th term is 0.5.
