A boat travels 12 km upstream and 40 km downstream in 8 hours. It can go 16 km upstream and 32 km downstream in the same time. Find the speed of the boat in still water and the speed of the stream.

Answers

Answer 1

the speed of the boat is 5.418 km/h and the speed of the stream is 2.167 km/h

Let's define the variables:

B = speed of the boat in still water.

S = speed of the stream.

When the boat travels downstream, the total speed of the boat will be equal to the sum of the speed of the stream and the speed of the boat in still water:

speed = B + S

When the boat goes downstream, the speed will be:

speed = B - S

Now, also remember the relation:

speed*time = distance.

The given information is:

In 8 hours the boat can:

go 12 km upstream and 40km downstream.

We now need to define another variable, T, as the time that the boat travels upstream.

Then we can write this as:

12km = (B - S)*T

If the boat travels T hours upstream, and travels for a total of 8 hours, then the amount of time that travels downstream is 8h - T, then we can write:

40km = (S + B)*(8h - T)

Similarly, when we have:

"it can go 16 km upstream and 32 km downstream in the same time."

we can define a new variable T', and write:

16km = (B - S)*T'

32km = (S + B)*(8h - T')

Then we have a system of 4 equations:

16km = (B - S)*T'

32km = (S + B)*(8h - T')

40km = (S + B)*(8h - T)

12km = (B - S)*T

And we need to solve this for S and B.

To do it, we need to isolate one of the variables in one of the equations.

Let's isolate T in the last equation:

T = 12km/(B - S)

now we can replace that in the third equation to get:

40km = (S + B)*(8h - 12km/(B - S))

So now we have 3 equations:

16km = (B - S)*T'

32km = (S + B)*(8h - T')

40km = (S + B)*(8h - 12km/(S - B))

Now we need to do the same thing, this time let's isolate T' in the first equation and replace it in the second one:

T' = 16km/(B - S)

Replacing it in the second equation we get:

32km = (S + B)*(8h - T')

32km = (S + B)*(8h - 16km/(B - S))

So now we have two equations:

40km = (S + B)*(8h - 12km/(B - S))

32km = (S + B)*(8h - 16km/(B - S))

Let's simplify these:

40km = 8h*(S + B) - 12km*(S + B)/(B - S)

32km = 8h*(S + B) - 16km*(S+ B)/(B - S)

Now we can multiply both equations by (B - S) to get:

40km*(S - B) = 8h*(S + B)*(B - S) - 12km*(S + B)

32km*(S - B) = 8h*(S + B)*(B - S) - 16km*(S+ B)

Let's keep simplifying this:

40km*(B - S) + 12km*(S + B) =  8h*(S + B)*(B - S)

32km*(B - S)  + 16km*(S+ B) = 8h*(S + B)*(B - S)

Now we get:

52km*B - 28km*S = 8h*(S^2 + B^2)

48km*B - 16km*S = 8h*(S^2 + B^2)

Notice that the right side of these equations is the same thing, then we can write:

52km*B - 28km*S = 48km*B - 16km*S

(52km - 48km)*B = (28km - 18km)*S

4km*B  =  10km*S

B = (10/4)*S

B = (5/2)*S

Now we can replace this in one of our two equations, let's use the first one:

48km*B - 16km*S = 8h*(S^2 + B^2)

48km*(5/2)*S - 16km*S = 8h*( S^2 + ( (5/2)*S)^2)

Now we can solve this for S

104km*S = 8h*( S^2 + 25/4*S^2)

104km*S = 8h*(29/4*S^2) = 48h*S^2

104km*S = 48h*S^2

dividing at both sides by S we get:

104km = 48h*S

104km/48h = S = 2.167 km/h

And using B = (5/2)*S

We can find the speed of the boat:

B = (5/2)*2.167 km/h = 5.418 km/h

Then:

the speed of the boat is 5.418 km/h and the speed of the stream is 2.167 km/h

If you want to learn more about this topic, you can read:

https://brainly.com/question/17300107


Related Questions

what is the range of the function y = 2x - 3 if the domain is 1

Answers

Answer:

1.5

Step-by-step explanation:

y=2x - 3

0 = 2x - 3

-2x = - 3 /÷(-2)

x = 3 ÷ 2

x = 1.5 3/2

a circle has a radius of 8.5cm correct to the nearest 0.1cm.
the lower bound of the area of the circle is pπ cm².
the upper bound of the area of the circle is qπ cm².

find the value of p and the value of q.

Answers

Answer:

The area of the circle is exactly π times the square of its radius. If you are given that the radius is within 0.1cm of 8.5cm, i.e. lies between 8.4 cm and 8.6 cm, its square will lie between p=8.4² = 70.56 and q=8.6² = 73.96 cm².

Answer:

The area of the circle is exactly π times the square of its radius. If you are given that the radius is within 0.1cm of 8.5cm, i.e. lies between 8.4 cm and 8.6 cm, its square will lie between p=8.4² = 70.56 and q=8.6² = 73.96 cm².

Step-by-step explanation:

thanks for question dear

the best way to learn math formulas

Answers

Writing down the formulas on charts and pasting it in your room,by seeing this daily it helps to memorize the formulas.

Saying the formulas louder also helps to memorize the formula.

Watching videos related to maths formulas and equations helps to remember the formulas easier.

Doing many problems regularly will helps you to remember the formulas.

lastly study to Understand The Formula not to memorize

A cylindrical paint can has a diameter of 12 centimeters and height of centimetrs which is closest to the volume of the paint can in cubic centimeters

Answers

Answer:

The correct answer is "1808.64 cm³".

Step-by-step explanation:

Seems that the given query is incomplete. Below find the attachment of the complete problem.

Given:

Diameter,

d = 12 cm

Radius,

r = [tex]\frac{d}{2}[/tex]

 = [tex]\frac{12}{2}[/tex]

 = [tex]6 \ cm[/tex]

Height,

h = 16 cm

As we know,

The volume of cylinder is:

= [tex]\pi r^2 h[/tex]

By substituting the values, we get

= [tex]3.16\times (6)^2\times 16[/tex]

= [tex]3.14\times 36\times 16[/tex]

= [tex]1808.64 \ cm^3[/tex]

Please hurry I will mark you brainliest

What is the equation of the line parallel to y = 2x - 4 and with the same x - intercept as 3x – 4y = 12?

Answers

Answer:

y=2x-8

Step-by-step explanation:

Hi there!

We want to find an equation of the line parallel to y=2x-4 but has the same x intercept as 3x-4y=12

Parallel lines have the same slope, but different y intercepts

In y=2x-4, which is written in y=mx+b form, m is the slope and b is the y intercept

2 is in the place of where the slope would be, so the slope of that line is 2

That means the slope of the line parallel to it would also have a slope of 2

Here is the equation of the parallel line so far:

y=2x+b

We need to find b, the y intercept

Typically, we'll substitute a point into the equation to solve for b, but we don't have a point, yet

We're given that the new line has the same x intercept as 3x-4y=12

The x intercept is the point where the line passes through the x axis, and so the value of y at that point is 0

Let's substitute 0 for y in 3x-4y=12 and solve for x to find the x intercept

3x-4(0)=12

Multiply

3x=12

Divide both sides by 3

x=4

So the value of the x intercept is 4. As a point, it's (4,0)

So now substitute the values of the point (4,0) into y=2x+b to find b

0=2(4)+b

Multiply

0=8+b

Subtract 8 from both sides

-8=b

Substitute -8 as b into the equation

y=2x-8

Hope this helps!  

write down amultiple of 4 and 14 which is less than 30​

Answers

28

How?

Multiples of 4=8,12,16,20,24,28Multiples of 14=28,42

We can see that 28 is the lowest common multiple also it is <30

Answer: 28.

Step-by-step explanation: 28 is divisible by 4: 28 / 4 = 7. 28 is divisible by 14: 28 / 14 = 2. And 28 is less than 30

Find the number in which 9 has greater value.
0.5689
5.6890
56.89
569.80

Answers

Answer:

569.80

Step-by-step explanation:

Among all the choices, the digit 9 has the greatest value in number 569.80. For the reason that 9 got ones value - which are greatest than other.

[tex]\tt{ \green{P} \orange{s} \red{y} \blue{x} \pink{c} \purple{h} \green{i} e}[/tex]

please help:

give an example of an undefined term and how it relates to a circle.​

Answers

It is the set of all points in a plane that are at a given distance from a fixed point.

A viewfinder has a triangular lens. Some of the measurements of the lens are
shown below. Which of the following best represents the length of a?
B
26°
a
С
389
10
A
Triangle not drawn to scale

Answers

Answer: Choice A) 6.8 inches

=========================================================

Explanation:

It's a bit strange why your teacher has the "26 degree" label pointing at a side length, rather than an actual angle. I'm assuming your teacher meant to aim it at angle C. In other words, I'm assuming they meant to say angle C = 26 degrees.

If that assumption is correct, then,

A+B+C = 180

38+B+26 = 180

B+64 = 180

B = 180-64

B = 116

Then we can use the law of sines like so:

a/sin(A) = b/sin(B)

a/sin(38) = 10/sin(116)

a = sin(38)*10/sin(116)

a = 6.84986152123146

a = 6.8

Side 'a' is approximately 6.8 inches long. So that's why the answer is choice A.

5. There are 5,280 feet in a mile. What part of a mile, in decimal form, will you drive until you reach the exit? I NEED THIS QUICK PLZ HELP I’LL GIVE YOU 30

Answers

Brainlist me!! :) hope this helps you

Answer:

5.280

Step-by-step explanation:

i did this question and got it

please someone answer! i need it rn!

Answers

The second one they do not have to pass trough (0,0)

Solve for X. Geometry

Answers

Answer:

x=12

Step-by-step explanation:

QS=QR+RS

2x-11=7+x-6

x=12

191+13=13+191191+13=13+191
what type of property is that

Answers

what nice question that we can understand ok

I’m not going to lie I don’t know what’s going on with this question

(x+4)^2 - (x-6)^2 - (x-1)*(x+1)

Answers

Answer:

-9

Step-by-step explanation:

amusement park is 1.50$ for children and $4 for adults. on certain day 220 people entered the park, and the admission fee collected totalled 630.00. how many children and how many adults were admitted? write and use an equation to solve

Answers

230.000 childrenㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

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ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ

Answer:

230 children

Step-by-step explanation:

A. Explain why the point (100,2) is on the graph.
B. What is the x-intercept of the graph? Explain how you know.
49
C. When will the graph meet the line y = 5? Explain how you know.

Answers

Answer:

the log function is the "inverse" function of an exponential function

by definition  [tex]log_{a} b = c[/tex]  then [tex]a^{c} = b[/tex]

in this problem you have [tex]log_{10} 100[/tex]

thus what x solves this ?  [tex]10^{x} = 100[/tex]  the answer is [tex]10^{2}[/tex]

thus (100,2)

B) the x intercept is when y = 0

   [tex]10^{0} = 1[/tex]

   x intercept at (1,0)

C) at 100, the curve will hit y = 5000

Step-by-step explanation:

Which relation is not a function?

Answers

Answer:

A

For something to be a function every x value bust have at most 1 y value and in A 9 has 2 y values so it cant be a function

four less than the product of a number and 7 is eight more than that number

Answers

Answer:

2

Step-by-step explanation:

Replace the number with x, then the equation would be:

7x-4=x+8

7x-x=8+4

6x=12

6x/6=12/6

x=2

A coin contains 9 grams of nickel and 161616 grams of copper, for a total weight of 25 grams.
What percentage of the metal in the coin is copper?

Answers

Answer:

64percents

Step-by-step explanation:

25-9=16 grams - weight of copper

(16/25)*100=64 percents

Pls help if u only know the correct answer!! Thanks!! :))

Answers

Answer:

3.5, 4.2

Step-by-step explanation:

reflect make it not negative and its on y axis so y not affected

Which is the equation of a parabola with Vertex (0,0) and focus (0, 2)?
a. ya = 8x
c. x2 = 8
b. y2 = 4x
d. x2 = 4y

Answers

Answer:

So the equation of the parabola is x2=8y i don't really know

I am not sure. Is this right?

Answers

Answer:

14.4

Step-by-step explanation:

since the longest side is 24,find the shortest side

√20^2-12^2

√400-144

√256

=16

which means the other shortest side is 24-16

which is 8

then you have to use the 12 and 8 to find the unknown side

√12^2+8^2

144+64

√208

14.4

I hope this helps

3a
[tex] \frac{3a + a {}^{2} }{a} [/tex]
Simplify. ​

Answers

Answer:

(3+a)

Step-by-step explanation:

3a + a^2

-------------

a

Factor out an a in the numerator

a(3+a)

-------------

a

Cancel like terms

(3+a)

Step-by-step explanation:

[tex] \frac{3a + {a}^{2} }{a} \\ = \frac{3a}{a} + \frac{ {a}^{2} }{a} \\ = 3 + a \\ thank \: you[/tex]

Find the nth term of the arithmetic
sequence - 1,2,5, ....

A. 3n - 2
B. -2n + 1
C. 2n + 2
D. 3n - 4

Answers

Answer:

3n -4

Step-by-step explanation:

We are adding 3 each time

-1+3 =2

2+3 = 5

The formula for an arithmetic sequence is

an = a1+d(n-1) where a1 is the first term and d is the common difference

an = -1+3(n-1)

    = -1 +3n -3

    = 3n -4

find the missing length indicated​

Answers

Answer:

192

Step-by-step explanation:

Apply the geometric mean formula to solve for x, which is the altitude of the right triangle.

The formula is:

h = √(mn)

h = x = ?

m = 144

n = 400 - 144 = 256

Substitute

h = √(256*144)

h = √36,864

h = 192

Therefore, x = 192

Which of the following statements best describes the relationship between
any point on an ellipse and each of its two foci?
A. The quotient of the distances to each focus equals a certain
constant.
B. The difference of the distances to each focus equals a certain
constant.
C. The sum of the distances to each focus equals a certain constant.
D. The product of the distances to each focus equals a certain
constant.

Answers

Answer:

C

Step-by-step explanation:

The sum of distances from any point on the ellipse to each foci equals a certain amount, no matter what point on the ellipse it starts from. The foci are on the major radius of the ellipse (the longer length of horizontal/vertical). The foci are of equal distance from the center, with one on each side.

If you wanted to find where the foci are using the major and minor radius, we can find that, representing the distance between the center and any foci as g,

g² = major radius² - minor radius². Then, the distance between the center and the foci is equal to g

state the following true or false ​

Answers

Answer:

c. false (it should always be neg.)

d. false

Step-by-step explanation:

Answer:

(c) True, (d) False

Step-by-step explanation:

If the order of two matrices are different, then the addition of matrices does not exists true or false

Answers

Answer:

true

Step-by-step explanation:

A matrix can only be added/subtracted with another matrix if the two matrices have the same dimensions

Question 11 of 25
If the point (1, 4) is on the graph of an equation, which statement
must be true?
A. There are solutions to the equation for the values x = 1 and
x = 4.
B. The values x = 1 and y = 4 are the only values that make the
equation true.
C. The values x = 4 and y= 1 make the equation true.
D. The values x = 1 and y = 4 make the equation true.
SUBMIT

Answers

Answer:

D

Step-by-step explanation:

simple : when we have a point defined as (1, 4), it means x = 1, y = 4.

and since the point is on the graph of a function/equation it means that when we use x = 1 and calculate the equation, we get 4 as result (= y). so yes, that means that both sides of the "=" sign are indeed equal for this pair of values, which makes the equation true.

but there will be usually many other pairs that do that too.

8TH GRADE MATH ¯\_(ツ)_/¯

What is the fractional equivalent of the repeating decimal n = 0.1515.... ?

Answer the questions to find out.

1. How many repeating digits does the number represented by n have?

2. You need to multiply n by a power of 10 to help you find the fraction. Decide on the power of 10 to multiply by, and tell how you identified that number.

3. Write an equation where the left side is your power of 10 time n and the right side is the result of multiplying 0.1515... by that power.

4. Write the original equation, n = 0.1515... underneath your equation from question 3. Then subtract the equations. Show your work!

5. Write n as a fraction in simplest form. Show your work!​

Answers

If n = 0.151515…, then 100n = 15.151515…

Then

100n - n = 15.151515… - 0.151515…

99n = 15

n = 15/99 = 5/33

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