Final answer:
To calculate the time the boat takes to row downstream, one must know the boat's speed in still water and the speed of the stream. The time downstream can be found by solving a set of equations derived from the known times and speeds. Without specific speeds, an exact numerical answer cannot be provided.
Step-by-step explanation:
Calculating Time to Row Downstream
Let’s solve the problem step by step. First, we know the boat rows a certain distance in still water in 35 minutes. The student asks how long the boat would take to row downstream if it takes 12 minutes less to row downstream than upstream. Now, let’s denote the speed of the boat in still water as Vboat, the speed of the stream as Vstream, the upstream time as Tup, and the downstream time as Tdown.
Since Tdown is 12 minutes less than Tup, we have:
Tup = Tdown + 12
Next, we use the fact that in still water the boat takes 35 minutes to row the distance. The speeds upstream and downstream are affected by the stream. Thus:
Speed Upstream:
Vboat - Vstream
Speed Downstream:
Vboat + Vstream
The time to cover a certain distance d is given by d divided by speed. So:
Time Upstream (Tup) = d / (Vboat - Vstream)
Time Downstream (Tdown) = d / (Vboat + Vstream)
From the given information we can calculate d as 35 min × Vboat. Using this distance to express Tup and Tdown, we get two equations. By solving these equations we can find Tdown, which is our final goal. It should be noted that in the question above, a specific value for the speed of the boat and the speed of the stream is not provided, so we cannot calculate an exact numerical value for Tdownsub> within this context. However, these steps outline a general approach to solving such a problem.