Answer:
b = [tex]\frac{45}{4}[/tex]
Step-by-step explanation:
given b is directly proportional to a, then the equation relating them is
b = ka ← k is the constant of proportionality
to find k, substitute b = 10, when a = 8 into the equation
10 = 8k ( divide both sides by 8 )
[tex]\frac{10}{8}[/tex] = k , that is
k = [tex]\frac{5}{4}[/tex]
b = [tex]\frac{5}{4}[/tex] a ← equation of proportion
when a = 9 , then
b = [tex]\frac{5}{4}[/tex] × 9 = [tex]\frac{45}{4}[/tex]
