A motorboat travels 81 miles in 3 hours going upstream. It travels 135 miles going downstream in the same amount of time. What is the rate of the boat in still water and what is the rate of the current?

Answer:

(a): x is 3 and ky is -1

(b): k is -2

Step-by-step explanation:

Let: 3x + ky = 8 be equation (a)

x - 2 ky = 5 be equation (b)

Then multiply equation (a) by 2:

→ 6x + 2ky = 16, let it be equation (c)

Then equation (c) + equation (b):

[tex] { \sf{(6 + 1)x + (2 - 2)ky = (16 + 5)}} \\ { \sf{7x = 21}} \\ { \sf{x = 3}}[/tex]

Then ky :

[tex]{ \sf{2ky = 3 - 5}} \\ { \sf{ky = - 1}}[/tex]

[tex]{ \bf{y = \frac{1}{2} }} \\ { \sf{ky = - 1}} \\ { \sf{k = - 2}}[/tex]

Simultaneous equations are used to represent a system of related equations.

The value of k when [tex]y = \frac 12[/tex] is -2

Given that:

[tex]3x + ky = 8[/tex]

[tex]x - 2ky = 5[/tex]

[tex]y = \frac 12[/tex]

Substitute [tex]y = \frac 12[/tex] in both equations

[tex]3x + ky = 8[/tex]

[tex]3x + k \times \frac 12 = 8[/tex]

[tex]3x + \frac k2 = 8[/tex]

[tex]x - 2ky = 5[/tex]

[tex]x - 2k \times \frac 12 = 5[/tex]

[tex]x - k = 5[/tex]

Make x the subject in [tex]x - k = 5[/tex]

[tex]x = 5 + k[/tex]

Substitute [tex]x = 5 + k[/tex] in [tex]3x + \frac k2 = 8[/tex]

[tex]3(5 + k) + \frac k2 = 8[/tex]

Open bracket

[tex]15 + 3k + \frac k2 = 8[/tex]

Multiply through by 2

[tex]30 + 6k + k = 16[/tex]

[tex]30 + 7k = 16[/tex]

Collect like terms

[tex]7k = 16 - 30[/tex]

[tex]7k = - 14[/tex]

Divide both sides by 7

[tex]k = -2[/tex]

Hence, the value of constant k is -2.

Read more about simultaneous equations at:

https://brainly.com/question/16763389

Answer:

A = 120

Step-by-step explanation:

Angle A is a vertical angle to 120 and vertical angles are equal

A = 120

[tex]\Large\rm\underbrace{{\green{ \: Angle \: A \: = \: 120 \degree}}}[/tex]

Because vertically opposite angles are always equal.

Answer:

7x = 42

Step-by-step explanation:

"Product" refers to multiplication and "is" refers to equal to.

Hi! I'm happy to help!

This equation will be written like this

x×7=42

To make this easier to solve, we can use the inverse operation, division.

42÷7=x

42 divided by 7 is 6, so the answer is 6.

I hope this was helpful, keep learning! :D

Answer:

Samuel had RM8 previously

Step-by-step explanation:

24÷3=8

Answer:

20 mm^3, 20 cubic millimeters

Step-by-step explanation:

The volume of a prism is length times width times height.

Length, width, and height can have units of mm.

mm * mm * mm = mm^3

The units of a volume must be cubic units.

Answer: 20 mm^3, 20 cubic millimeters

9514 1404 393

Answer:

  2/3

Step-by-step explanation:

Let x represent the fraction of Cheryl's income she spent in September. Then 1-x is the fraction she saved.

In October, her spending increased by 0.2x, and her savings decreased by 0.4(1 -x). Since Cheryl spends or saves all of her income, these two change amounts must be equal:

  0.2x = 0.4(1 -x)

  x = 2(1 -x) . . . . . . multiply by 5 to clear fractions

  x = 2 -2x . . . . . . eliminate parentheses

  3x = 2 . . . . . . . . add 2x

  x = 2/3 . . . . . . divide by 3

Cheryl spent 2/3 of her income in September.

Answer:

x^2, 10-x , 1.5x -5  

Step-by-step explanation:

Step-by-step explanation:

Concept Required :-

Brackets , Of , Division , Multiplication , Addition , Subtraction .

Solution 9:-

We are here given ,

Putting brackets after and before 10 -8

On simplifying,

Expression :- 32 ÷ (10 -8) ÷ 2 - 3

Solution 10 :-

We are given,

Putting brackets ,

Expression :- 1/2 × (12 ÷ 2 - 2 ) +11

Step-by-step explanation:

1. 32 ÷ 10 - 8 ÷ 2 - 3

32 ÷ 2 ÷ 2 - 3

16 ÷ 2 - 3

8 - 3

5

2.

½ × 12 + 2 - 2 + 11

6 + 2 - 2 + 11

19 - 2

17

Answer: [tex]x = \pm2\sqrt{7}\\\\[/tex]

Work Shown:

[tex]x^2 = 28\\\\x = \pm\sqrt{28}\\\\x = \pm\sqrt{4*7}\\\\x = \pm\sqrt{4}*\sqrt{7}\\\\x = \pm2\sqrt{7}\\\\[/tex]

This can be rewritten into [tex]x = 2\sqrt{7} \ \text{ or } \ x = -2\sqrt{7}[/tex]

Answer:

1/2

Step-by-step explanation:

Filling out the tree diagram,

On the first throw, there is a 4/4 = 100%* chance Jennifer hits or misses. Therefore, the chance she misses is equal to the difference between

(chance she hits or misses) - (chance she hits) = 4/4 - 1/4 = 3/4

For the second throw, the chance she hits is independent of whether she hits or misses on the first throw. This means that it does not matter whether she hits or misses on the first throw; her chance to hit the second throw will always be 1/3. Therefore, 1/3 can go into the hit category on each hit line on the second throw, and in the miss category, we can put

100% - 1/3 = 1 - 1/3 = 3/3 - 1/3 = 2/3

For Jennifer to hit the bullseye at least once, she must either:

- Hit and then hit

- Hit and then miss

- Miss and then hit

From this, we can determine that if Jennifer hits the first bullseye, she will have hit it at least once, no matter what. Therefore, Jennifer must either:

- Hit the first one

- Miss and then hit

In probability, OR /either means that we add the probabilties. The probability that she hits the first one is 1/4, and the probability that she misses and then hits is

(probability she misses the 1st one) * (probability she hits the second one). We know to multiply here because both scenarios must happen, and for AND probabilities, we multiply. We thus have

(3/4) * (1/3) = 3/12 = 1/4 as the probabilty that she misses then hits, and 1/4 as the probability that she hits the first one. We add these up to get 1/4 + 1/4 = 2/4 = 1/2 as our probability that she hits the bullseye at least once

* we know 4/4 = 100% because 100% = 1, and anything divided by itself is equal to 1.

Answer:

Step-by-step explanation:

Jocelyn was attempting to find out how much she will be charged per download. She has the fraction upside down. To find the amount of money per download, the fraction should be $12/3downloads to get $4/1download. That is the slope of the equation, the rate of change or, for us, the fact that your cost will go up $4 for every single video you download. The equation would then be

y = 4x

The way she has it, we are paying only a quarter for a download. If that be the case, for 3 downloads we would only be paying .75, but it says we pay $12, so we know something is wrong right there.

Answer:

The answer is A

Step-by-step explanation:

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

Explanation:

1/2 = 4/8 after multiplying top and bottom by 8

So the mixed number 7  1/2 is the same as 7  4/8

We can convert to an improper fraction like so

7  4/8

7 + 4/8

7*(8/8) + 4/8

56/8 + 4/8

(56+4)/8

60/8

Notice how dividing 60 over 8 leads to 7 remainder 4. Think of it like having 60 cookies and you want to share them amongst 8 friends. Each friend gets 7 whole cookies (7*8 = 56 taken so far) and then we have 60-56 = 4 left over as the remainder.

Through similar steps, you should find that the mixed number 1  7/8 converts to the improper fraction 15/8.

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

To rephrase the problem with improper fractions would be to say:

"The electrician needs to buy 60/8 feet of wire. There are 15/8 feet of wire in each spool. How many spools should the electrician buy?"

Let x be the answer to that question.

We multiply the number of spools (x) by the amount of feet of wire per spool (15/8) to get the expression (15/8)x

Set this equal to the target 60/8 and solve for x

(15/8)x = 60/8

15x = 60 .... multiply both sides by 8 to clear out the fractions

x = 60/15

x = 4

The electrician needs to buy exactly 4 spools

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

A different approach could have us convert each mixed number into decimal form

7  1/2 = 7 + 1/2 = 7 + 0.5 = 7.5

1  7/8 = 1 + 7/8 = 1 + 0.875 = 1.875

So the electrician needs to buy 7.5 ft total and each spool has 1.875 ft of wire.

Using the same idea as before, we would then have,

1.875x = 7.5

x = (7.5)/(1.875)

x = 4

Answer:  1 unit

Explanation:

The diameters are 6 and 8, which cut in half to 3 and 4 respectively.

The difference in these radii values is 4-3 = 1.

This is the distance from one circle's edge to the other circle's edge, such that we're on the same line that goes through the center of the circles. This is the gap width or ring width so to speak.

Answer:

No solution.

Step-by-step explanation:

[tex]6m-m=\frac{5}{6}(6m-10)\\5m=5m-\frac{25}{3}\\0\neq -\frac{25}{3}[/tex]

Therefore, there is no solution.

Answer:

105

Step-by-step explanation:

25 days = Food for 630 men

30 days = x           (Inverse variation)

30 * x = 630 * 25

x = 630 * 25/30

  = 21 * 25

  = 525 men.

630 - 525 = 105 men.

Therefore, 105 men must be transferred to another camp so that the food lasts for 30 days.

Answer/Step-by-step explanation:

1. To find the area of the shaded region, you'd find the area of the white rectangular shape, next, find the area of the whole triangular shape, then find the difference of their areas to get the area of the shaded region. Thus, the formula to use would be:

Area of shaded region = area of triangle - area of rectangle

Area of shaded region = ½*base*height - length*width

1. a. Volume of triangular prism = area of triangular base * height of prism

Volume of triangular prism = ½bh * H

Where,

b = 6 m

h = 4 m

H = 8 m

Substitute

Volume of prism = ½*6*4*8

Volume of prism = 96 m³

b. Volume of sphere = ⁴/3πr³

Where,

r = 9 cm

Substitute

Volume = ⁴/3*π*9³

Volume = ⁴/3*π*729

Volume ≈ 3,053.6 cm³ (nearest tenth)

2. Use Pythagorean theorem to find the height of the cone

radius of the cone (r) = ½(16) = 8 cm

Slant height (l) = 11 cm

height (h) = ?

Using Pythagorean theorem, we have:

h = √(l² - r²)

Substitute

h = √(11² - 8²)

h = √(57)

h ≈ 7.5 cm (nearest tenth)

b. Volume of the cone = ⅓πr²h

where,

r = 8 cm

h = 7.5 cm

Volume = ⅓*π*8²*7.5

Volume = 502.7 cm³ (nearest tenth)

Answer:

C: 119 square inches

Step-by-step explanation:

We are given;

Slant height; L = 5 in

Base area; B = 49 in²

Since it's a square pyramid, the base portion has a square shape.

Thus, area of base = x²

Where x is a side of the square.

Thus;

x² = 49

x = √49

x = 7

Perimeter of base = 7 × 4 = 28 in

Area of pyramid = ½PL + B

Plugging in the relevant values;

Area of pyramid = (½ × 28 × 5) + 49

Area of pyramid = 119 in²

Answer:

Step-by-step explanation:

The formula for slope is y2-y1/x2-x1 where y2 and x2 are the x and y coordinates from a coordinate pair and y1 and x1 are the coordinates from another coordinate pair. In this case, 2 coordinate pairs are given: (30,75) and (10, 35)  75-35/30-10 would be your slope, or, 40/20, or simplified, 2.

Your slope is 2

Answer:

7

Step-by-step explanation:

Going from -5 to 2 we get

1) -4

2) -3

3) -2

4) -1

5) 0

6) 1

7) 2

So, in total, there are 7 numbers between -5 and 2

Answer:

There are 0.454 kg in one pound.

So, in 120 pounds there are 0.454 x 120 kgs.

This is equal to 54.48, and the answer is 54.48 kg.

Let me know if this helps!

Answer:

x = 2

Step-by-step explanation:

Answer:

6.52 x 10^3 is just basically 6.52 × 1000, which is 6520. But 652,000 ÷ 10^2 is just 652000 ÷ 100, which is 6520. That's why they have the same answer.

Answer:

37.5%

Step-by-step explanation:

Calculation to determine the theoretical probability that the tree is not within the acres of apple trees

Using this formula

P=(Number of all orchard acres - Apple acres)/(Total orchard acres)*100

Where,

P represent Probability

Let plug in the formula

P=(40 acres- 25 acres)/40 acres

P=15 acres/40 acres *100

P=3/8*100

P=.375*100

P=37.5%

Therefore the THEORETICAL PROBABILITY that the tree is not within the acres of apple trees is 37.5%

Answer:

the answer is 37.5

Step-by-step explanation:

it is

The equation of the circle whose center is (0, 0) and whose radius 5 is x² + y² = 25.

A circle can be characterized by its center's location and its radius's length.

Let the center of the considered circle be at (h,k) coordinate.

Let the radius of the circle be 'r' units.

Then, the equation of that circle would be:

(x-a)²+(y-b)² = r²

Where (a, b) is the centre and 'r' is the radius

We have a circle with centre (0, 0) and radius of 5.

Now, Substituting these value into the equation form, we have

(x-0)²+(y-0)² = 5²

x² + y² = 25

Hence, the equation of the circle whose center is (0, 0) and whose radius 5 is x² + y² = 25.

Learn more about equation of a circle here:

https://brainly.com/question/10165274

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Answer:

A

Giải thích:

f(1)=f(x)

f(-1) và f(-2)= f(-x)

=> f(1)=f(-1) =A. f(x)=f(-x)

Answer:

Step-by-step explanation:

The basic 30-60-90 triangle ratio is:

Side opposite to 30° angle is : x

Side opposite to 60° angle is : x √3

Side opposite to 90° angle is : 2x

From the diagram we learn that

x√3 = 10

[tex]x = \frac{10}{\sqrt{3}}=\frac{10*\sqrt{3} }{\sqrt{3}*\sqrt{3}}\\\\x=\frac{10\sqrt{3}}{3}= 5.77\\[/tex]

∠T = 30°, Side opposite to ∠T is AC = 5.77

∠A = 90°, side opposite to ∠A is TC = 2x = 2*5.77 = 11.54

Answer:

Step-by-step explanation:

The central angle of a hexagon is 60 degrees. Drop a line from the center to the middle of the side marked 7.

Use the  tan of the angle so formed (which is 30 degrees)

Tan(30)= opposite / height (which is the line you just drew).

Tan(30) = 3.5 / h

Tan(30) = 0.5774

Tan(30) = 3.5 / h                multiply both sides by h

h*Tan(30) = 3.5                  Divide by tan30

h = 3.5 / Tan(30)

h = 3.5 / 0.5774

h = 6.062

Now from both ends of the given side, draw 2 lines to the center. Find the area of that triangle.

Area of 1 triangle = 1/2 * b * h

area of 1 triangle = 1/2 * 7 * 6.062

Area of 1 triangle = 21.2176

There are 6 such triangles so multiply that number by 6

Answer:  6 * 21.2176

Answer:  127.31

Answer:

Đáp án:

60km

Step-by-step explanation:

30 phút

=

1

2

giờ

Ô tô đi từ A đến B rồi từ B về A mất số thời gian là:

10

−

6

−

1

2

=

3

,

5

giờ (không tính thời gian nhận hàng)

Gọi độ dài quãng đường AB là

x

(km)

Ta có:

Thời gian đi từ A đến B là

x

40

(quãng đường chia vận tốc)

Thời gian đi từ B đến A là

x

30

Ta có phương trình:

x

40

+

x

30

=

3

,

5

⇔

x

=

60

(km)

Vậy quãng đường AB là 60km.