Respuesta :
The speed of the current in a river if a boat moves at 20 miles/hour in still water is 6 miles per hour
Solution:
Formula for downstream:
If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then:
Speed downstream = (u + v) km/hr
Given that boat moves at 20 miles/hour in still water
Speed of boat in still water = 20 miles per hour
The boat takes 3 hours to travel 78 miles downstream
Let us find the speed of downstream
The formula for speed is given as:
[tex]speed = \frac{distance}{time}[/tex]
[tex]\text{ speed downstream } = \frac{78}{3} = 26 \text{ miles per hour }[/tex]
Thus speed downstream is 26 miles per hour
Let "v" be the speed of current
Let "u" be the speed in still water
Given, u = 20 miles per hour
Then by above mentioned formula,
Speed downstream = (u + v) miles per hour
26 = 20 + v
v = 26 - 20
v = 6
Thus speed of current in river is 6 miles per hour
