We have that the time it takes the boat to make a round trip consisting of a 250 m displacement downstream followed by a 250 m displacement upstream
T=70sec
From the question we are told
A boat moves through a river at 7.5 ms relative to the water, regardless of the boat's direction.
If the water in the river is flowing at 1.5 ma. how long does it take the boat to make a round trip consisting of a 250 m displacement downstream followed by a 250 m displacement upstream?
Generally the equation for the Time taken is mathematically given as
[tex]t=\frac{d}{v_1+v_2}t=\frac{250}{7.5+1.5}t=28s[/tex]
Where
Time taken to go upstream
[tex]t'=\frac{d}{v_1-v_2}\\\\t'=\frac{250}{7.5-1.5}\\\\t'=42s[/tex]
Therefore
[tex]T=t+t'\\\\T=28+42[/tex]
T=70sec
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