Arowing team rowed 90 miles while going with the current in the same amount of time as it took to row 10 miles going against the current. the rate of the
current was 4 miles per hour. find the rate of the rowing team in still water.
rate of the team in still water:

The speed in still water is 5 miles per hour.

Step-by-step explanation:

distance with current = 90 miles

distance against current = 10 miles

speed in still water = s

speed of current = 4 mph

speed with current = s + 4

speed against current = s - 4

time = t

speed = distance/time

distance = speed * time

With current:

90 = (s + 4) * t

Against the current:

10 = (s - 4) * t

We have a system of equations:

90 = (s + 4) * t

10 = (s - 4) * t

90 = ts + 4t

10 = ts - 4t

Subtract the second equation from the first equation.

80 = 8t

10 = t

t = 10

10 = t(s - 4)

10 = 10(s - 4)

1 = s - 4

s = 5

The speed in still water is 5 miles per hour.

d. is the correct answer

step-by-step explanation:

tell you what. i'll find the length of the medians and you can fill in the blanks where they belong.

br

b = (2a,0)

r = (a/2,b/2) remember these things are medians. they go to the 1/2 way point of the line opposite the vertex they face.

br^2 =   (2a - a/2)^2 + (0 - b/2)^2

br^2 = (3/2 a) ^2 + b^2 / 4

br^2 = 9/4 a^2 + b^2 / 4   we need to find some relationship between a and b.

let's try ab = bc  

ab = 2a

bc = (2a - a)^2 + (b - 0)^2

bc = sqrt(a^2 + b^2)

ab = bc

2a = sqrt(a^2 + b^2) square both sides.

4a^2 = a^2 + b^2 subtract a^2 from both sides.

sqrt(3a^2) = sqrt(b^2)

sqrt(3)a = b

let's put b into br^2

br^2 = 9/4 a^2 + 3b^2 / 4

br^2 = 12 a^2 / 4

br^2 = 3a^2 

br = sqrt(3) * a

cp

c = (a,b) ; p = (a,0) this is another application of the distance formula, and it is a good one.

cp^2 = (a - a)^2 + (b - 0)^2

cp^2 = 0 + b^2

cp^2 = b^2 which you can see from the diagram. 

cp = sqrt(b^2)

cp = b but b = sqrt(3) * a 

cp = sqrt(3)*a

aq

a = (0,0)

q = (3/2) a, b/2

aq^2 = (3a/2 -0)^2 + (b/2 - 0)^2

aq^2 = 9a^2/4 + b^2/4

but b = sqrt(3) * a 

aq^2 = 9a^2 / 4 + (sqrt(3)*a)^2 /4

aq^2 = 9 a^2/ 4 + 3 a^2 / 4

aq^2 = 12 a^2/4

aq^2 = 3 a^2

aq = (sqrt  3) * a which agrees with the other two.