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Ymorist [56]
3 years ago
13

A racing shell, which is a boat a crew team rows, moves 20 km/h in still water. During practice, the team rows 36 km against the

current and 22 km with the current. Find the speed of the river current if the team rows a total of 3 hours.
Mathematics
2 answers:
saveliy_v [14]3 years ago
4 0

Answer:

2 km/h

Step-by-step explanation:

Let x represent the speed of the river current, t₁ be the time spent rowing against the current and t₂ be the time spent rowing with the current.

Since the speed of the still water = 20 km/h.

The speed of rowing against the current = (20 - x)

The speed of rowing with the current = (20 + x)

We know that velocity = distance / time. Hence time = distance / velocity

t₁ = 36 / (20 - x)

t₂ = 22 / (20 + x)

but t₁ + t₂ = 3 hours

Therefore:

3 = 36 / (20 - x) + 22 / (20 + x)

multiply through by 400 - x²

3(400 - x²) = 36(20 + x) + 22(20 - x)

1200 - 3x² = 720 + 36x + 440 - 22x

3x² + 14x -40 = 0

This gives x = -6.7 or x = 2

x cannot be negative therefore x = 2 km/h

The speed of the river current is 2 km/h

Ann [662]3 years ago
4 0

Answer:

2km/h is correct

Step-by-step explanation:

The other guy is absolutely correct

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sukhopar [10]

Answer: I and III

Step-by-step explanation:

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3 0
3 years ago
Hii I need help with these questions tyy!
9966 [12]

Answer:

(7x+2)(3x-1); (5x+4)^2 or (5x+4)(5x+4);

Step-by-step explanation:

formula to find area is L* W = A ; meaning length multiplied by width equals to the area.

21.

using the formula to find area...

l*w=a

(7x+2)(3x-1) would be your answer

btw, don't put the "=a" at the end, since it's an expression :))

22.

since the problem states that it's a square, you can just say either...

(5x+4)^2 or (5x+4)(5x+4) not sure which one your teacher accepts

4 0
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Answer:

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Step-by-step explanation:

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Yuliya22 [10]

Answer:

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Answer:

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