Question 391876
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Hi
Let x represent
Determining 'hat size' from the size of the head is an excellent example of 
a direct proportion between Hat size and Head circumference.
that is: hat size = k*Head size OR k =hat size/head size , where k is a constant.
{{{k[in] =7.25/22.8in = .318}}} Or hat size = .318*head size(in)
{{{k[cm] =7.25/58cm = .125}}}  OR hat size = .12*head size(cm)

Hat size 7 1/8  (7.125)
(7 1/8) = .318*head size(in) 
 7.125/.318 = 22.4in
(7 1/8) = .125*head size(cm) 
7.125/.125 = 57cm