Answer:
5 km/h
Step-by-step explanation:
In this problem, Lashonda swam 4 km against the current. So the distance covered in this case is
[tex]d_1=4 km[/tex]
Calling [tex]v[/tex] the velocity of Lahonda without the current, and [tex]c[/tex] the velocity of the current, in this situation Lahonda's velocity is
[tex]v-c[/tex]
So we can write:
[tex]t_1=\frac{d_1}{v-c}[/tex]
where [tex]t_1[/tex] is the time taken to cover the distance.
When Lashonda swims with the current, her velocity is
[tex]v+c[/tex]
So we can write
[tex]t_2=\frac{d_2}{v+c}[/tex]
where
[tex]d_2=16 km[/tex] is the distance covered in this case, and [tex]t_2[/tex] the time taken.
The velocity of the current is
[tex]c=3 km/h[/tex]
Since Lashonad takes the same time to cover the two distances,
[tex]t_1=t_2[/tex]
So we can write
[tex]\frac{d_1}{v-c}=\frac{d_2}{v+c}[/tex]
And solving for v, we find Lashonda's velocity without the current:
[tex]d_1(v+c)=d_2(v-c)\\d_1 v+d_1c = d_2v-d_2c\\v(d_2-d_1)=c(d_1+d_2)\\v=\frac{d_2+d_2}{d_2-d_1}c=\frac{16+4}{16-4}(3)=5 km/h[/tex]
