A boat takes time t₁ to travel a fixed distance downstream and time t₂ to return the same distance upstream. If u is the boat speed relative to water and v is the stream speed, then v/u is:
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A boat takes time t₁ to travel a fixed distance downstream and time t₂ to return the same distance upstream. If u is the boat speed relative to water and v is the stream speed, then v/u is:

G1 Physics · Accepted Answer

For distance L: u + v = L/t₁ and u - v = L/t₂. Subtracting and adding these equations gives v/u = [(1/t₁) - (1/t₂)]/[(1/t₁) + (1/t₂)] = (t₂ - t₁)/(t₁ + t₂).