[tex]\dfrac{90}2=45[/tex]
[tex]\dfrac{135}3=45[/tex]
[tex]\dfrac{225}5=45[/tex]
[tex]\dfrac{270}6=45[/tex]
The constant of proportionality is thus 45; the unit rate is 45 miles per hour.
The relationship between the time t (in hours) and the distance d (in miles) is thus [tex]d=45\cdot t[/tex]
