Answer:
r = 2.5
Step-by-step explanation:
given the equation y = rx ← r is the constant of proportionality
then r = [tex]\frac{y}{x}[/tex]
from the given values of x and y
r = [tex]\frac{25}{10}[/tex] = [tex]\frac{12.5}{5}[/tex] = [tex]\frac{10}{4}[/tex] = 2.5
