yes, it vary directly with the time, because:
[tex]\begin{gathered} \text{let:} \\ h=\text{height} \\ t=\text{time} \\ h(t)=kt \\ \text{Where:} \\ k=\text{constant of proportionality} \end{gathered}[/tex]For t = 5 , h = 70
so:
[tex]\begin{gathered} 70=k\cdot5 \\ k=\frac{70}{5} \\ k=14 \end{gathered}[/tex]If:
[tex]\begin{gathered} t=7\colon \\ h(7)=14\cdot7=98 \\ t=10\colon \\ h(10)=14\cdot10=140 \\ t=15\colon \\ h(15)=14\cdot15=210 \end{gathered}[/tex]Since there is a constant of direct proportionality for each of the values, the function varies directly
