Question

question 4 (1 point)
a boat can move at 30 km/h in still water. how long will it take to move 12 km upstream in a river flowing 6.0 km/h?
20 min
22 min
24 min
30 min

Explanation:

Step1: Calculate the upstream speed

The formula for upstream speed \(v_{up}\) is \(v_{boat}-v_{river}\). Given \(v_{boat} = 30\space km/h\) and \(v_{river}=6\space km/h\), then \(v_{up}=30 - 6=24\space km/h\).

Step2: Use the formula \(t=\frac{d}{v}\)

We know \(d = 12\space km\) and \(v = v_{up}=24\space km/h\). Substituting into the formula \(t=\frac{d}{v}\), we get \(t=\frac{12}{24}h\). Since \(1h = 60min\), then \(t=\frac{12}{24}\times60min\).

Answer:

\(24\space min\)