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.

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

2km/h is correct

Step-by-step explanation:

The other guy is absolutely correct

c. y = 1/4 x + 5

step-by-step explanation:

first, put the equation of the line on the graph into slope-intercept form

(y = mx + b):   y = -4x + 8

second, a perpendicular line has to have "an opposite/reciprocal slope" to the original slope. so, find the "m" value in your original equation (it's -4, right? )

original slope: m = -4   perpendicular slope: change the sign to its opposite and find the reciprocal ("flip" the number)

new slope is now positive (b/c the original slope was negative 4), and it's 1/4 (not the original slope of 4 or 4/1)