[tex3]\Delta{t}=\frac{S}{V_1}[/tex3] -> [tex3]50=\frac{S}{V_1}[/tex3]
[tex3]\Delta{t_2}=\frac{S}{0,8V_1}[/tex3] -> [tex3]0,8t_2=\frac{S}{V_1}=50[/tex3]
[tex3]0,8t_2=50[/tex3] -> [tex3]t_2=\frac{50}{0,8}[/tex3] -> [tex3]t_2=62,5[/tex3]
[tex3]62,5=62:30[/tex3]