Final answer:
To calculate last year’s winning speed in a boat race, only the time is needed because the question already provides the boat's speed. Using the formula speed = distance/time, average speed can be determined if both time and distance are known.
Step-by-step explanation:
To calculate last year’s winning speed, the necessary information is the boat's speed and the time taken to complete the race. Since the distance traveled is equal to the rate (boat’s speed) times the time, knowing both the speed and the time will allow us to determine the speed of last year's winner. Nonetheless, because we are calculating speed which is already given as a rate, we only need the time to calculate the average speed for the entire journey as per the formula speed = distance/time.
If we are given the distance and the time it took to complete that distance, we can divide the two to calculate average speed. As per the information provided, if we are reassessing the speed for last year's race, the distance is known, being the length of the course. Hence, if we have the time tally for the race, we can compute the winning boat's average speed.