Chapter P, Prerequisites - Section P.1 - Modeling the Real World with Algebra - P.1 Exercises - Page 5: 10

Answer: A). P = 103.68 hp B). s = 5 knots

Here P = 0.06$s^{3}$ P is power in horse power s is speed in knots A). here s=12 knots. i.e. P = 0.06$\times12^{3}$ = 0.06 $\times$ 1728 = 103.68 hp B). here P = 7.5 hp i.e. $s^{3}$ = $\frac{7.5}{0.06}$ = 125 i.e s = $\sqrt[3] 125$ = 5 knots