🔍 Key Concepts

• Relationship between ship speed and fuel consumption, often approximated using a power of the speed (for displacement hulls, fuel ∝ speed³ is a common exam assumption) • How to set up a ratio or proportion when one quantity changes based on another raised to a power • Careful unit consistency: same ship, tons per hour at different speeds

💭 Think About

• Ask yourself: if fuel burned per hour is proportional to the cube of the speed, how can you express the new fuel rate in terms of the old rate and the ratio of the speeds? • Write an equation using the initial condition (8 tons/hour at 15 knots) and apply the speed change to 21 knots, then compare: what factor does the fuel rate increase by? • After calculating the new tons/hour, which of the answer choices is numerically closest to your computed value?

✅ Before You Answer

• Confirm you are using the same time unit (per hour) for both fuel rates • Verify you are using the ratio of speeds correctly (21/15) before applying the exponent • Double-check your calculator steps: compute the speed ratio first, raise it to the appropriate power, then multiply by 8 tons/hour