Question

6. A boat with speed of 1.20 km/h relative to the water is heading for a dock 2.29

km downstream. If the river speed is 0.384 km/h, how many minutes will it take
to reach the dock?​

Answer 1

Answer: 87 min

Step-by-step explanation:

The speed of the boat
`S_(boat)` will be its speed relative to the river
`S_(boat-river)` plus the the speed of the river
`S_(river)`:

`S_(boat)=S_(boat-river)+S_(river)` (1)

`S_(boat)=1.20 km/h+0.384 km/h` (2)

`S_(boat)=1.584 (km)/(h)` (3)

On the other hand, the speed of the boat is given by a relation between its traveled distance
`d` and the time
`t`:

`S_(boat)=(d)/(t)` (4)

Isolating
`t` and knowing
`d=2.29 km`:

`t=(d)/(S_(boat))` (5)

`t=(2.29 km)/(1.584 (km)/(h))` (6)

`t=1.445 h (60min)/(1 h)=86.74 min \approx 87 min` (7)

Hence the time in minutes is 87 min.