Answer: 87 min
Explanation:
The speed of the boat [tex]S_{boat}[/tex] will be its speed relative to the river [tex]S_{boat-river}[/tex] plus the the speed of the river [tex]S_{river}[/tex]:
[tex]S_{boat}=S_{boat-river}+S_{river}[/tex] (1)
[tex]S_{boat}=1.20 km/h+0.384 km/h[/tex] (2)
[tex]S_{boat}=1.584 \frac{km}{h}[/tex] (3)
On the other hand, the speed of the boat is given by a relation between its traveled distance [tex]d[/tex] and the time [tex]t[/tex]:
[tex]S_{boat}=\frac{d}{t}[/tex] (4)
Isolating [tex]t[/tex] and knowing [tex]d=2.29 km[/tex]:
[tex]t=\frac{d}{S_{boat}}[/tex] (5)
[tex]t=\frac{2.29 km}{1.584 \frac{km}{h}}[/tex] (6)
[tex]t=1.445 h \frac{60min}{1 h}=86.74 min \approx 87 min[/tex] (7)
Hence the time in minutes is 87 min.
