\(\dfrac{90}2=45\)
\(\dfrac{135}3=45\)
\(\dfrac{225}5=45\)
\(\dfrac{270}6=45\)
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 \(d=45\cdot t\)
