You have steamed 499 miles at 21 knots and are burning 462 barrels of fuel per day. You must decrease your consumption to 221 barrels per day with 311 miles left in your voyage. What must you reduce your speed (kts) to in order to burn this amount of fuel?
• Fuel consumption is often assumed proportional to the CUBE of speed in these exam problems • You can compare the ratio of old fuel consumption to new fuel consumption to find the ratio of old speed to new speed • Use the relationship between distance, speed, and time: Distance = Speed × Time
• First, find how many days it took to travel the first 499 miles at 21 knots, then how many barrels per day that represents in proportion to your target 221 barrels/day • Set up a proportion that relates (old speed / new speed)^3 to (old consumption / new consumption) and solve for the new speed • Once you find a candidate new speed, check if the time to travel the remaining 311 miles at that speed makes sense for the voyage scenario
• Verify the assumed relationship: fuel consumption ∝ (speed)^3 for this type of exam problem • Carefully compute the ratio of current consumption (462 bbl/day) to target consumption (221 bbl/day) before doing any cube roots • After finding a possible speed, confirm that it is one of the multiple-choice options and is less than 21 knots, since you are reducing consumption
No comments yet
Be the first to share your thoughts!