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To do this, you need to form equations using the information given. There are 2 variables here, the base speed of the rower with no current (x), and the speed of the current (y).

Firstly, convert the distances and times given into average speeds.

20km/2 hours = 10km/h

4km/2 hours = 2km/h

The actual speed = the base speed +- the current, depending on direction.

So 10 = x + y

2 = x - y

If we subtract these 2 equations to eliminate x, we get:

8 = 2y

y = 4km/h

Q: A person can row downstream 20km in 2 hours and upstream 4km in 2 hours. find the speed of the current?

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The speed upstream is B - C where B is the speed of the badge in still water and C is speed of the current The speed downstream is B + C. Velocity = Distance/Time : therefore Time = Distance/Velocity. Time for upstream journey = 6/(B - C) Time for downstream journey = 6/(B + C) BUT Total time for journey = 2 = 6/(B - C) + 6/(B + C) = 12B/(B2 - C2) Therefore 2B2 - 2C2 = 12B : However, B = 8kph so substituting gives, 128 - 2C2 = 96 : 2C2 = 32 : C2 = 16 : C = 4 The speed of the current is 4kph.

Call the unknown speed of the current c and the speed of the boat in still water b. When travelling upstream, the net speed of the boat will be b - c and when travelling downstream the net speed of the boat will be b + c. Since b = 4c, the speed upstream will be 3c. The distance upstream is one-half the total travelling distance of 150 km or 75 kilometers. Distance travelled = speed X time at speed, so that upstream time = 75/3c, downstream time = 75/5c, and the sum of these is the total time stated to be 8 hours. Thus 75/3c + 75/5c = 8. Multiplying both sides by 15c yields 75(5 +3) = 120c, or c = (8 X 75)/120 = 5 kilometers per hour.

Suppose the speed of the boat is x mph. Then upstream, it travels 5 hours at x-3 mph and so covers 5x - 15 miles. When going downstream the boat covers the same distance, at x+3 mph, in 2.5 hours so (5x-15)/(x+3) = 2.5 Multiply through by 2*(x+3): 2*(5x-15) = 5*(x+3) 10x - 30 = 5x + 15 or 5x = 45 giving x = 9 mph.

The average speed downstream is 40 ÷ 4 = 10 mph. However, it would seem that insufficient information has been supplied to enable a satisfactory answer to this question to be provided.

Let s = unknown speed in still water in units of miles per hour. The downstream speed will then be s + 4 and the upstream speed s - 4. In an equal time t in units of hours, t(s+4) = 40 and t(s-4) = 24. Multiplying out the parenthetical expressions yields ts + 4t = 40 and ts - 4t = 24. Subtracting the second of these equations from the first gives 8t = 16, or t = 2 hours. Therefore, ts +4t = 40, by substituting 2 for t becomes: 2s + 8 = 40, or 2s = 40 - 8 = 32, or s = 16 miles per hour.

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Velocity = Distance ÷ Time.The speed upstream = 300 ÷ 5 = 60kph.The speed downstream = 300 ÷ 2 = 150 kph.The speed upstream equals boat velocity(Vb) minus current velocity(Vc).The speed downstream equals boat velocity (Vb) pluscurrent velocity (Vc).Vb - Vc = 60Vb + Vc = 150 : Adding the two equations together gives :-2Vb = 210 : Vb = 105, therefore Vc = 45The rate of the boat in still water is 105 kph. The rate of the current is 45 kph.

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The speed upstream is B - C where B is the speed of the badge in still water and C is speed of the current The speed downstream is B + C. Velocity = Distance/Time : therefore Time = Distance/Velocity. Time for upstream journey = 6/(B - C) Time for downstream journey = 6/(B + C) BUT Total time for journey = 2 = 6/(B - C) + 6/(B + C) = 12B/(B2 - C2) Therefore 2B2 - 2C2 = 12B : However, B = 8kph so substituting gives, 128 - 2C2 = 96 : 2C2 = 32 : C2 = 16 : C = 4 The speed of the current is 4kph.

Boats speed = 24 miles per hour.Current speed = 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.

It is 5 miles per hour.

Call the unknown speed of the current c and the speed of the boat in still water b. When travelling upstream, the net speed of the boat will be b - c and when travelling downstream the net speed of the boat will be b + c. Since b = 4c, the speed upstream will be 3c. The distance upstream is one-half the total travelling distance of 150 km or 75 kilometers. Distance travelled = speed X time at speed, so that upstream time = 75/3c, downstream time = 75/5c, and the sum of these is the total time stated to be 8 hours. Thus 75/3c + 75/5c = 8. Multiplying both sides by 15c yields 75(5 +3) = 120c, or c = (8 X 75)/120 = 5 kilometers per hour.

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.

Suppose the speed of the boat is x mph. Then upstream, it travels 5 hours at x-3 mph and so covers 5x - 15 miles. When going downstream the boat covers the same distance, at x+3 mph, in 2.5 hours so (5x-15)/(x+3) = 2.5 Multiply through by 2*(x+3): 2*(5x-15) = 5*(x+3) 10x - 30 = 5x + 15 or 5x = 45 giving x = 9 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

The speed of the boat is 36 km/h. Going upstream: 3h x 36km/h = 108 km, minus (6x3 =18 km) = 90 km Going downstream: 2h x 36km/h = 72 km, plus (6x2 =12 km) = 90 km

The average speed downstream is 40 ÷ 4 = 10 mph. However, it would seem that insufficient information has been supplied to enable a satisfactory answer to this question to be provided.