To find the time Jack takes to cross Swan Lake, his average speed is required:
The time it will take Jack to cross Swam Lake is 0.5 hours
Reason:
Time it took Jack to paddle 6.4 km upstream, t = 2 hours
Distance Jack paddled, d = 6.4 km
The given speed of the Black River, v₂ = 1.8 km/h
The width of the lake, w = 2.5 km
The time it will take Jack to cross Swan Lake
Let v₁, represents Jack's speed, we have;
[tex]v_1 - v_2 = \dfrac{d}{t}[/tex]
Therefore;
[tex]v_1 - 1.8 = \dfrac{6.4}{2} = 3.2[/tex]
v₁ = 3.2 + 1.8 = 5
[tex]Time \ to \ cross \ the \ lake , \ t_S = \dfrac{w}{v_1}[/tex]
[tex]t_S = \dfrac{2.5 \, km}{5 \, km/h} = 0.5 \, hr.[/tex]
The time it will take Jack to cross Swan Lake, [tex]t_S[/tex] = 0.5 hours
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