Let boat speed = X and current speed = Y
Downstream speed = boat speed plus current speed = X + Y
Upstream speed = boat speed minus current speed = X -Y
Downstream speed = 2 miles divided by 3 minutes = 2/3 miles per minute
Upstream speed = 2 miles divided by 15 minutes = 2/15 miles per minute
X + Y = 2/3
X - Y = 2/15
add equations
2X = 2/3 + 2/15 = 10/15 + 2/15 = 12/15 = 4/5
divide by 2
X = 4/10 = 2/5
use second equation and find Y as
X -Y = 2/15
2/5 - Y = 2/15
6/15 - Y = 2/15
Y = 4/15 = current speed = 0.266 miles per minute
1.4 x 3 = 4.2 miles Note: 20 minutes = 1.4 miles : 40 minutes = 2.8 miles : 60 minutes (1 hour) = 4.2 miles
3 miles in 22 2 minutes is the same speed as 15 miles per 110 minutes.
.5 miles in .8 minutes = 5 miles in 8 minutes = 5/8 miles per minute = 0.625 miles per minute or 37.5 miles per hour..5 miles in .8 minutes = 5 miles in 8 minutes = 5/8 miles per minute = 0.625 miles per minute or 37.5 miles per hour..5 miles in .8 minutes = 5 miles in 8 minutes = 5/8 miles per minute = 0.625 miles per minute or 37.5 miles per hour..5 miles in .8 minutes = 5 miles in 8 minutes = 5/8 miles per minute = 0.625 miles per minute or 37.5 miles per hour.
50 miles in 10 minutes is the same as 300 miles per hour, since 50 miles/10 minutes * 60 minutes/1 hour = 300 miles per hour
13.1 miles in 110 minutes is about 8.5 minutes per mile.
The current is approximately 4 mph.
To find how long it will take to return downstream, first determine the effective speed while rowing upstream. The current speed is 2 mph, so your effective speed upstream is your rowing speed minus the current. If it takes 3 hours to row 9 miles upstream, your rowing speed is 5 mph (since 9 miles / 3 hours = 3 mph, and 3 mph + 2 mph = 5 mph). While returning downstream, your effective speed will be 5 mph + 2 mph = 7 mph. Thus, it will take 9 miles / 7 mph = approximately 1.29 hours, or about 1 hour and 17 minutes, to return downstream.
2 Miles An Hour.
Boats speed = 24 miles per hour.Current speed = 4 miles per hour.
The gradient of the River Amazon is very low. It is 1,000 miles or 1,610 kilometers upstream, and 100 feet or 30 meters downstream.
8 MPH
Speed upstream(S.u) = 20/5 => 4miles/hr Speed downstream(S.d) = 10/2 => 5miles/hr Speed of man in still water(speed of boat in still water)= 1/2 * (S.u + S.d) = 0.5 * (4 + 5) = 0.5 *9 = 4.5miles/hr The speed of man in still water is 4.5 miles/hr
Her average speed is 1.6 miles per hour. Average speed is total distance covered by total time taken to do it. She swims 4 miles upstream, and at 1 mph, it takes 4 hours. She comes back downstream at 4 mph and so she covers the 4 miles in 1 hour. Her total mileage is 8 miles. It takes 4 + 1 hours or 5 hours to cover it. The 8 miles divided by 5 hours is 1 3/5 miles per hour, or 1.6 mph for an average speed.
The current speed is about 4 miles per hour.
Since the distance downstream (with the current) equals the distance upstream (against the current), and if we: Let B stand for the speed (rate in mph) of the boat in still water, and using the formula rate X time = distance, the equation will be: (B+7) x 3 = (B-7) x 5 3B + 21 = 5B - 35 56 = 2B B = 28 mph Traveling downstream, the current will cause the boat to go faster so the 7 mph current is added to the boat's still water speed. Traveling upsteam the current slows or decreases the boat's rate so the current's speed is subtracted from the boat's still water speed.
assume river velocity = X mph boat velocity = 20 mph time to go 6 miles downstream = T1 time to go 3 miles upstream = T2 distance = time * velocity downstream: 6 mi = T1 * (boat velocity + river velocity) upstream: 3 mi = T2 * (boat velocity - river velocity) 6 = T1 * ( 20 + X ) 3 = T2 * ( 20 - X ) T1 * ( 20 + X ) = 2 * ( T2 * ( 20 - X ) ) since T1 = T2 then 20 + X = 40 - 2X 3X = 20 X = 6.67 thus, river velocity is 6.67mph
5.2 Miles, 13 minutes. However, in current traffic it will take about 18 minutes.