You are steaming at 19 knots and burning 440 barrels of fuel per day. You must decrease your consumption to 137 barrels per day. What must you reduce your speed to in order to burn this amount of fuel?

Correct Answer: Option D — 12.9

To reduce fuel burn from 440 to 137 barrels per day, apply the cube law for vessel propulsion: $V_2 = V_1 \times \sqrt[3]{F_2 / F_1}$. Substituting the values gives $19 \times \sqrt[3]{137 / 440}$, calculating out to exactly 12.9 knots.