A boat can go 25 km upstream in 5 hours. If the speed of the boat in still water

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Question: A boat can go 25 km upstream in 5 hours. If the speed of the boat in still water is 7 km/h, what is the speed of the stream?

Options:

Correct Answer: 2 km/h

Solution:

Let the speed of the stream be x km/h. Upstream speed = (7 - x) km/h. Therefore, 25/(7 - x) = 5. Solving gives x = 2 km/h.

A boat can go 25 km upstream in 5 hours. If the speed of the boat in still water is 7 km/h, what is the speed of the stream?

A boat can go 25 km upstream in 5 hours. If the speed of the boat in still water is 7 km/h, what is the speed of the stream?

Correct Answer: 2 km/h

Step 1: Understand that the boat's speed in still water is 7 km/h.
Step 2: Let the speed of the stream be x km/h.
Step 3: When the boat is going upstream, its effective speed is reduced by the speed of the stream. So, the upstream speed is (7 - x) km/h.
Step 4: We know the boat travels 25 km upstream in 5 hours.
Step 5: Use the formula: Speed = Distance / Time. Here, Speed = 25 km / 5 hours = 5 km/h.
Step 6: Set up the equation: (7 - x) = 5, because the upstream speed we calculated is 5 km/h.
Step 7: Solve for x: 7 - x = 5.
Step 8: Rearranging gives x = 7 - 5.
Step 9: Calculate x: x = 2 km/h.
Step 10: Conclude that the speed of the stream is 2 km/h.

Relative Speed – Understanding how the speed of a boat changes when moving against the current of a stream.
Algebraic Manipulation – Solving equations to find unknown variables, in this case, the speed of the stream.