How many ways are possible to select a president and vice president from an

An exterior angle of a regular convex polygon is 40°. What is the number of sides of the polygon?

seraphim [82]

Answer:

option B

Step-by-step explanation:

Sum of interior angles of a polygon with n sides:

$= (n - 2 )\times 180$

$Therefore, Each \ interior \ angle = (\frac{n - 2}{n} )\times 180$

$Sum \ of \ one \ of \ the \ interior \ angle \ with \ its \ exterior \ angle \ is \ 180^\circ$

$[ \ because \ straight \ line \ angle = 180^\circ \ ]$

That is ,

$Exterior \ angle + Interior \ angle = 180^\circ\\\\40^ \circ + (\frac{n-2}{n}) \times 180 = 180^\circ\\\\40 n + 180n - 360 = 180n\\\\40n = 180n - 180n + 360 \\\\40n = 360 \\\\n = 9$

OR

Sum of exterior angles of a regular polygon = 360

Given 1 exterior angle of the regular polygon is 40

Therefore ,

$n \times 40 = 360\\\\n = \frac{360}{40} \\\\n = 9$

8 0

3 years ago

Mrs Tan bought 4 times as many pens as notebooks and each notebook cost $8.20 more than each pen. She spent $26 more on the book

lilavasa [31]

Let x be the cost of 1 pen
then cost of 1 notebook = x + 8.20

Let y be the number of pens Tan buys
then number of notebooks Tan buys = y/4

She spent $26 more on books than on pens which means

Cost of notebooks - Cost of pens = 26
(x + 8.20) * y/4 - xy = 26

Sinplifying it

(xy + 8.20y)/4 - xy = 26
(xy + 8.20y - 4xy)/4 = 26
8.20y - 3xy = 104

She spent $394 which means

Cost of notebooks + Cost of pens = 394
(x + 8.20) * y/4 + xy = 394

Simplifying it

(xy + 8.20y)/4 + xy = 394
(xy + 8.20y + 4xy)/4 = 394
8.20y + 5xy = 1576

Now, we have two equations,

(1) 8.20y - 3xy = 104
(2) 8.20y + 5xy = 1576

Now we need to find a third equation with either x or y as the subject of any of both the previous equations.

Let's make y the subject of (2) equation

8.20y + 5xy = 1576
y(8.20 + 5X) = 1576
(3) y = 1576/(8.20 + 5x)

Let's substitute the new value of y from (3) into (1) because we rearranged (2) to from (3)

8.20y - 3xy = 104
y(8.20 - 3x) = 104
y = 104/(8.20 - 3x)
1576/(8.20 + 5x) = 104/(8.20 - 3x)
1576 * (8.20 - 3x) = 104 * (8.20 + 5x)
12923.2 - 4728x = 852.8 + 520x
12923.2 - 852.8 = 4728x + 520x
12070.4 = 5248x
12070.4/5248 = x
x = 2.3

Now find the value of y by substituting the value of x in either equation, preferably (3)

y = 1576/(8.20 + 5x)
y = 1576/(8.20 + 5 * (2.3))
y = 80

Therefore cost of 1 notebook = x + 8.20 = 2.3 + 8.20 = $10.50

8 0

3 years ago

3. Which is a function?

OverLord2011 [107]

Answer:

C) {(12,3), (11,2), (10,1), (9,0), (8,1), (7,2), (6,3)} Is a function.

Step-by-step explanation:

The easiest way to tell if a Relation is a Function (in my opinion) is the Verticle Line test. Use your pairs and put them in a graph. Then connect the dots, and if your line at any point touches the graph once, then your Relation is a Function. If it touches the graph more than once, it is not a Function.

Regards!

4 0

3 years ago

10)

Kipish [7]

Answer:

-600

Step-by-step explanation:

The rate of change of a function f(x) in a certain interval $(x_1,x_2)$ is the ratio between the change of the function and the change in the value of x:

$r=\frac{f(x_2)-f(x_1)}{x_2-x_1}$

The rate of change of a function tells how much the value of the function is changing per change in unit of x: therefore, for a linear function it corresponds to the slope of the line.

In this problem, the function f(x) is equal to the value of the business machine in dollars, while the variable x represents the number of years.

Here we are told that the machine was purchased for

$q=\$4500$

while its value decreases by $600 each year, so

$m=-600\$$

This means that the linear function that represents the value of the machine after x years is:

$y=4500-600x$

Therefore, the rate of change of the function is -600.

3 0

3 years ago

-8(6-r)=24 what is the solution for r

Andreas93 [3]

Answer:hi

Step-by-step explanation:Let me first warn you that I CANNOT get the denominators of this problem to go underneath the numerators. It looks good on my answer page but when I click "preview your answer" the denominators are ALL over the place. Grrrrr.

I think the weirdly placed denominators make this explanation hard to understand but you give this a go and see if you understand things. If it is too hard to see, maybe this website will let you instant message me or email me. If so, then I will send you the solution via email. I'm very sorry the denominators are SO scattered.

See what you think of the explanations below but it might help if you write down my answer on paper, so that you can move the number to rest more closely under their proper numerators. :-)

Ok then......

Let's start with your first problem. A quick way to do this work is to cross multiply. Here's what I mean:

__3___ = __6___

r - 1 r + 2

Ok, so you can cross multiply:

3(r + 2) = 6(r - 1) (cross multiply)

3r + 6 = 6r - 6 (use the distributive property)

Now you will have to put the "r" variables on the left side of the equal sign and numbers without variables on the right side of the equal sign. To get 6r from the right side to the left, you can subtract 6r from the right side. If you subtract it from the right, you must subtract it from the left.....

To get 6 from the left side to the right, you can subtract it from the left. If you subtract it from the left, you must subtract it on the right.....

So now you have:

3r - 6r = -6 - 6 This becomes.........

- 3r = -12

Now to solve for "r" you will have to divide by -3. Why? Well, -3r is really saying: -3 times r. The -3 and the r are actually being multiplied together so to isolate the "r" you have to sort of "undo" the multiplication. What is the opposite of multiplication? It's DIVISION. Soooo, you must divide by -3 on both sides. SO you have:

- 3r = -12

r = 4 (-12 divided by -3 is a positive 4)

Now you know "r" equals 4. If we "plug" 4 back into the original equation, we can see the answer is correct. Check this out:

__3___ = __6___ (original equation)

r - 1 r + 2

__3___ = __6___ (substitute "4" in for "r"

4 - 1 4 + 2

__3___ = __6___ (do the math in the denominator area)

3 6

1 = 1 (3/3 equals 1 and 6/6 also equals 1, so our

solution that r = 4 is correct!) :-)

Now to your 2nd problem..........

4/2x-5 = 24/2x

___4___ = __24___

2x � 5 2x

Let's cross multiply again:

4(2x) = 24(2x - 5)

8x = 48x - 120

8x - 48x = - 120

-40x = - 120

(divide both sides by -40)

x = 3

Now let's "plug" 3 in where we had the variable "x" in the original equation to see if we are correct.

___4___ = __24___ (original equation)

2x � 5 2x

___4___ = __24___ (substituted 3 for "x")

2(3) � 5 2(3)

___4___ = __24___

6 - 5 6

___4___ = __24___

1 6

4 = 4

SO once again we have found the correct answer. Yay for us! :-)

I hope this helps. :-)

8 0

3 years ago

Read 2 more answers