One centimenter is 0.01 meters. So, you can write the measures as
[tex] 152.40\text{m},\quad 205.10\text{m},\quad 310.39\text{m}[/tex]
Once this rewriting is done, getting the total length [tex]T[/tex] is quite trivial, since all measurements are in the same unit, and we can simply sum everything:
[tex]T = 152.40+205.10+310.39 = 667.89[/tex]
