Chapter 3 - 3.5 - Mathematical Modeling and Variation - 3.5 Exercises - Page 296: 63

Mathematical model: $y=2.5385x$ If $x=10~in$ $y=25.385~cm$ If $x=20~in$ $y=50.7692~cm$

$y=kx$ When $y=33~cm$, $x=13~in$: $33=k(13)$ $k=\frac{33}{13}\approx2.53846$ Then: $y=2.5385x$ If $x=10~in$ $y=2.53846\times10=25.385~cm$ If $x=20~in$ $y=2.53846\times20=50.7692~cm$