The telephone numbers in a small town have two digits. They run from 00 to 99.

Of the 100 possible numbers, those that become smaller when reversed are not used, i.e. 21 is not used.

What is the maximum number of telephone numbers this town could have?

Answers

Answer 1

Answer:

[tex]55[/tex]

Step-by-step explanation:

We'll be using case-work to solve this problem. Let's call the ones digit of the telephone number [tex]B[/tex] and the tens digit [tex]A[/tex]. Each telephone number can be represented as [tex]AB[/tex].

Since the question states that numbers that are smaller when their digits are reversed are not used, we have the following inequality:

[tex]B\geq A[/tex]

This is because if [tex]A>B[/tex], the number would become smaller when [tex]A[/tex] and [tex]B[/tex] are switched in [tex]AB[/tex]. However, if [tex]A=B[/tex] or [tex]B>A[/tex], the number will not become smaller.

Let's work our way up starting with [tex]A=0[/tex]. If [tex]A=0[/tex], there are 10 other numbers (0-9) that we can choose for [tex]B[/tex] that adhere to the condition [tex]B\geq A[/tex]:

[tex]0B,\\01, 02, 03,...[/tex]

Therefore, there are 10 possible telephone numbers when the tens digit is 0.

Repeat the process, now assigning [tex]A=1[/tex]. Now, we only have the digits 1-9 to choose from for [tex]B[/tex], since [tex]B[/tex] needs to be greater than or equal to A. Therefore, there are 9 possible telephone numbers when the tens digit is 1.

This pattern continues. As we work our way up through the cases (when increasing [tex]A[/tex] by 1), the number of possible telephone numbers decreases by 1, since there becomes one less option for [tex]B[/tex].

The last case would be [tex]A=9[/tex] in which case there would only be one option for [tex]B[/tex] and that would be 9.

Since there are 10 cases (0-9), add up the possible telephone numbers for each case:

[tex]\displaystyle \sum_{n=1}^{10}n=1+2+3+4+5+6+7+8+9+10=\boxed{55}[/tex]

Alternatively, recall that the sum of this series can be found using [tex]\frac{n(n+1)}{2}[/tex], where [tex]n[/tex] is the number of values in the set. In this case, [tex]n=10[/tex], and we have:

[tex]1+2+3+4+5+6+7+8+9+10=\frac{10(11)}{2}=\frac{110}{2}=\boxed{55}[/tex]


Related Questions


Which number is a solution of the inequality?
3x - 15 ≥ 3

a.) -9/11

b.)6/11

c.)6

d.)5

Answers

Answer:

6

Step-by-step explanation:

[tex]3x - 15 \geqslant 3[/tex]

[tex]3x \geqslant 3 + 15[/tex]

[tex]x \geqslant \frac{18}{3} [/tex]

[tex]x \geqslant 6[/tex]

according to the rational root theorem which of the following are possible roots of the polynomial function below? F(x)=6x^3-7x^2+2x+8

Answers

Answer:

Hello,

Step-by-step explanation:

all potential roots are of the form a/b where a is a divisor of 8

and b is a divisor of 6 ( in Z)

So A,D,E,F may be roots

but B and C not.

The distributive property can be applied to which expression to factor 12x3 – 9x2 + 4x – 3?
3(4x3– 1) – (9x2 + 4x)
4x(3x2 + 1) – 3(3x2 – 1)
3x(4x – 3) – (3+ 4x)
3x2(4x – 3) + 1(4x – 3)
IM ON EDGE

Answers

Answer:

12x^3-9x^2+4x-3

3(4x^3-1)-(9x^2+4x)

therefore option A is right

thank you, and mark it as brainliest if u find it useful

Apples are cut into 8 pieces to be shared among some children. Twenty-two bags of seven apples are used. How many pieces of apple are cut?

Answers

Answer: 1232 pieces

Work Shown:

1 bag = 7 apples

22 bags = 22*7 = 154 apples

So we have 154 apples to work with in total.

Each of those apples is cut into 8 pieces, giving us 8*154 = 1232 pieces

We can write it as one single calculation to say 22*7*8 = 1232

evelins room has an area of 45 squar feet. the length of her room is 5. what is the perimeter of her room?

Answers

Answer:

28 feet

Step-by-step explanation:

Since the area is 45 and length is 5.In order to find the width we divide the area by the side given

45 ÷ 5 = 9 is the width

Perimeter is the sum of all the side of a figure.

9 + 9 + 5 + 5

= 28

I hope this helps :)

Question 2 Evaluate the expression 2(x - 3) + 3y when x = 5 and y = 3. Mark the correct answer.
A. 13
B. 15
C. 16
D. 25​

Answers

Answer:

A. 13

Step-by-step explanation:

2(x - 3) + 3y

2(5 - 3) + 3×3

2× 2 + 3×3

4 + 9

13

Answer:

The correct answer is A

Step-by-step explanation:

2(x-3) + 3y so you replace them and get 2( 5 - 3) +3(3)

next,

you would solve it

2 x 5 and 2 x 3 you get 10-6 + 9, the 9 is from multiplying 3 by 3

finally you solve it

10-6 = 4 +9

= 13!

Which shapes have the greatest area?
(Select all that apply.)

Answers

Answer:

the trapiezium

Step-by-step explanation:

It has a area of 4 which is the highest

Write the equation of the line that passes through the points (−7,5) and (-7,-8).
Put your answer in fully reduced point-slope form, unless it is a vertical or horizontal line.

Answers

Answer:

x = -7

Step-by-step explanation:

First we find the slope using

m = ( y2-y1)/(x2-x1)

   = ( -8 - 5)/( -7 - -7)

   = (-8-5)/(-7+7)

   = -13/0

This means the slope is undefined and the line is vertical

Vertical lines are in the form

x= constant and the constant is the x value of the points

x = -7

Below are two different functions, f(x) and g(x). What can be determined about their slopes? f(x)= 4x + 2 The function g of x going through 0, negative 2 and 1, 3 (1 point) The function f(x) has a larger slope. The function g(x) has a larger slope. They both have the same slope. The relationship between slopes cannot be determined.

Answers

Answer:

g(x) has the larger slope.

Step-by-step explanation:

f(x) = 4x + 2

- so its slope = 4.      ( from general form y = mx + c where m = slope).

The slope of g(x) = (3 - (-2) / (1 - 0)

= 5.

for the function g(x)=3-8(1/4)^2-x

a) State the y-intercept

b) State the equation of the horizontal asymptote

c) State whether the function is increasing or decreasing.

d) State the domain and range
e) Sketch the graph

Could anyone help?

Answers

Using function concepts, it is found that:

a) The y-intercept is y = 2.5.b) The horizontal asymptote is x = 3.c) The function is decreasing.d) The domain is [tex](-\infty,\infty)[/tex] and the range is [tex](-\infty,3)[/tex].e) The graph is given at the end of the answer.

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

The given function is:

[tex]g(x) = 3 - 8\left(\frac{1}{4}\right)^{2-x}[/tex]

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

Question a:

The y-intercept is g(0), thus:

[tex]g(0) = 3 - 8\left(\frac{1}{4}\right)^{2-0} = 3 - 8\left(\frac{1}{4}\right)^{2} = 3 - \frac{8}{16} = 3 - 0.5 = 2.5[/tex]

The y-intercept is y = 2.5.

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

Question b:

The horizontal asymptote is the limit of the function when x goes to infinity, if it exists.

[tex]\lim_{x \rightarrow -\infty} g(x) = \lim_{x \rightarrow -\infty} 3 - 8\left(\frac{1}{4}\right)^{2-x} = 3 - 8\left(\frac{1}{4}\right)^{2+\infty} = 3 - 8\left(\frac{1}{4}\right)^{\infty} = 3 - 8\frac{1^{\infty}}{4^{\infty}} = 3 -0 = 3[/tex]

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

[tex]\lim_{x \rightarrow \infty} g(x) = \lim_{x \rightarrow \infty} 3 - 8\left(\frac{1}{4}\right)^{2-x} = 3 - 8\left(\frac{1}{4}\right)^{2-\infty} = 3 - 8\left(\frac{1}{4}\right)^{-\infty} = 3 - 8\times 4^{\infty} = 3 - \infty = -\infty[/tex]

Thus, the horizontal asymptote is x = 3.

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

Question c:

The limit of x going to infinity of the function is negative infinity, which means that the function is decreasing.

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

Question d:

Exponential function has no restrictions in the domain, so it is all real values, that is [tex](-\infty,\infty)[/tex].From the limits in item c, the range is: [tex](-\infty,3)[/tex]

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

The sketching of the graph is given appended at the end of this answer.

A similar problem is given at https://brainly.com/question/16533631

Darryl has written 60 percent, or 12 pages, of his history report. Darryl wants to figure out how many total pages he needs to write. Darryl’s work is shown below.
Step 1: Write 60 percent as a ratio. StartFraction part Over whole EndFraction = StartFraction 60 Over 100 EndFraction

Answers

Answer:

total pages = 20

Step-by-step explanation:

60% of an unknown number is 12

Let the unknown number (total pages) be x.

60/100 of x = 12

60/100 * x = 12

3/5 x = 12

x = 12 * 5/3

x = 20

Total page equals 20 your welcome my friend

If g(x) = 2(x − 4), find the value of x if g(x) = 20

Answers

Answer:

x=14

Step-by-step explanation:

g(x) = 2(x − 4)

Let g(x) = 20

20 = 2(x − 4)

Divide each side by 2

20/2 = 2(x-4)/2

10 = x-4

Add 4 to each side

10+4 = x-4+4

14 =x

PLEASE HELP ASAP!!!!! The following graph shows a proportional relationship. What is the constant of proportionality between y and x in the graph?

Answers

Answer:

2/3

Step-by-step explanation:

The graph point is on (3,2)

PLS HELP WILL MAKE FIRST RIGHT ANSWER GETS BRAINLIEST ​

Answers

Answer:
26. A
27. A

Explanation:

Find the measure of the indicated angle to the nearest degree.

Answers

Answer:

Step-by-step explanation:

Adjacent to the undetermined angle is 6, and the hypotenuse has been given. We can conclude, after looking at our SOHCAHTOA, that we will be using cosine(CAH) to solve this problem.

Let the unspecified angle be [tex]\theta\\[/tex] (This sign is called theta, which is just a sign for angle)

Lets start!

cos[tex]\theta\\[/tex] = adj/hyp

cos[tex]\theta\\[/tex] = 6/13

[tex]\theta\\[/tex] = [tex]cos^{-1}[/tex](6/13)

[tex]\theta\\[/tex] = 62.5

[tex]\theta\\[/tex] = 63

Hope that helped!

Find the area of this circle. Use 3 for .
A = r2
12 cm
[?] cm2

Answers

Answer:

452.16 cm²

Step-by-step explanation:

Given :-

Radius = 12cm .

To find :-

Area of circle .

Solution :-

As we know that ,

A = πr² A = 3.14 * (12 cm)² A = 3.14 * 144cm² A = 452.16 cm²

Step-by-step explanation:

[tex]area = \pi {r}^{2} \\ = \pi \times {12}^{2} \\ = \pi \times 144 \\ = 3.14 \times 144 \\ = 452.16 {cm}^{2} \\ thank \: you[/tex]

A P E X fasted answer is getting 30 points please hurry.

suppose a normal distribution has a mean of 98 and a standard deviation of 6. what is p(x ≥ 92)

Answers

Answer:

Step-by-step explanation:

If the mean is 98 and standard deviation is 6, then 92 is one standard deviation to the left of the mean; that means that 34% + 34% + 13.5% + 2.35% + .15% of the data is included in this area. Add those up and you get, as a percentage, 84%.

Answer:

0.84

Step-by-step explanation:

yee its right

find the measure of one exterior angle for the following regular polygon ​

Answers

Answer:

36 degrees

Step-by-step explanation:

10 corners/sides.

the sum of all exterior angles in a polygon is always 360 degrees.

so, one exterior angle here is 360/10 = 36 degrees

Solve for x: -5 < 8x + 11 < 19

Answers

Answer:

-2<x<1

Step-by-step explanation:

-5 < 8x + 11 < 19

Subtract 11 from all sides

-5-11 < 8x + 11-11 < 19-11

-16 < 8x<8

Divide by 8

-16/8 < 8x/8 <8/8

-2<x<1

PLS HELP ME RN I AM FAILING AND NEED HELP ITS PYTHAGOREAN THEOREM

Answers

Answer:

9.89949 or 9.9

Step-by-step explanation:

7^2 + 7^2 = c^2

49+49=98

square root of 98 = 9.89949

Pythagoren theorem is a^2 + b^2 = c^2

In this case 7^2 + 7^2 =c^2

49 + 49 = 98^2

But you dont want the second number squared so you find the square root if it. In this case square root 98 = 9.899494937

Since it say round to the nearest tenth however it will look more like this 9.9

Good Luck

What is the value of the expression below when w=2 and x=2
9w - x

Answers

Here, all we need to do is subtitute w = 2 and x = 2 into the expression, by multiplying and adding. First, we will muliply 9w:

9w

9 · w =

9 · 2 =

18

Now, all we have to do is use our answer for 9w, and subtract x from it:

9w - x

18 - (2) =

18 - 2 =

16

So, our answer is 16.

Let me know if you have any other questions! :)

This equation shows how the total number of necklaces Denise owns is related to the amount of money she spends on additional necklaces.

n = d + 74

The variable d represents the amount of money she spends on additional necklaces, and the variable n represents the total number of necklaces she owns. With $16 to spend on new necklaces, how many total necklaces can Denise own?

Answers

answer: n=90

please mark brainliest

Which of the following planets has the strongest winds in the solar system?
O Jupiter
O Mars
O Neptune
O Venus

Answers

Neptune has the strongest winds in the Solar System. Winds whip clouds of frozen methane across the planet at speeds of more than 1,200 miles per hour (2,000 kilometers per hour).

Answer: The answer is Neptune ^-^

Step-by-step explanation:

Got it correct on the test :]

Fastest answer will be declared the brainliest

Answers

Answer:

All whole numbers are rational numbers.

False

All integers are whole numbers.

True

There are integers that are not rational numbers.

True

There are whole numbers that are not integers.

True.

The volume of this cube is 64 cubic feet. What is the value of a?

Answers

Answer:

a = 4 feet

Step-by-step explanation:

Since it's a cube, we know that each value will be equal. Because of this, you can cube root the cube's volume to find a.

[tex]\sqrt[3]{64}=4[/tex]

Therefore, a = 4 feet.

Answer:

4

Step-by-step explanation:

To find the area of a cube, we have to multiply the width, height, and length, which, since they are all the same value, would be a side multiplied by itself 3 times(cubed). So, the area of this cube in terms of a(side) is a*a*a or a^3. The area is given to be 64, so we can write:

a^3 = 64

With the equation, we can realize 4*4*4 is 64, meaning a is 4.

9/7 = please answer me​

Answers

Answer:

[tex] \frac{9}{7} = 1.2857 = 1 \frac{2}{7} [/tex]

Answer:

Step-by-step explanation:

[tex]\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\la\la\la\la\ddddddddddddddddddddddddddddddddcleverdddddd\ffffffffffffffffffffffffffffffffffffffff\pppppppppppppppppppppppppppppppppppp\ddddddddddddddddddd\displaystyle\ \Large \boldsymbol {\frac{9}{7}=1\frac{2}{7} \ \ or \ \ 1.(28571)}[/tex]

Complete the table, and then use the drawing tools to create the graph representing the relationship between the amount of plant food remaining, f(x), and the number of days that have passed, x.

Answers

The complete table of the function is:

[tex]\begin{array}{cccccccc}x & {0} & {1} & {2} & {3} & {4}& {5} & {6} \ \\ f(x) & {72} & {60} & {48} & {36} & {24}& {12} & {0} \ \end{array}[/tex]

The equation missing from the question is:

[tex]y = 72 - 12x[/tex]

To complete the table, we simply calculate the y value for each x value;

When [tex]x = 0[/tex],     [tex]y = 72 - 12 * 0 = 72[/tex]

When [tex]x = 1[/tex],     [tex]y = 72 - 12 * 1 = 60[/tex]

When [tex]x = 2[/tex],     [tex]y = 72 - 12 * 2 = 48[/tex]

When [tex]x = 3[/tex],     [tex]y = 72 - 12 * 3 = 36[/tex]

When [tex]x = 4[/tex],     [tex]y = 72 - 12 * 4 = 24[/tex]

When [tex]x = 5[/tex],     [tex]y = 72 - 12 * 5 = 12[/tex]

When [tex]x = 6[/tex],     [tex]y = 72 - 12 * 6 = 0[/tex]

So, the complete table is:

[tex]\begin{array}{cccccccc}x & {0} & {1} & {2} & {3} & {4}& {5} & {6} \ \\ f(x) & {72} & {60} & {48} & {36} & {24}& {12} & {0} \ \end{array}[/tex]

To create a graph of f(x), we simply type [tex]y = 72 - 12x[/tex] on a drawing tool and the graph will be generated.

See attachment for graph

Learn more about graphs at:

https://brainly.com/question/20106471

Answer:

Step-by-step explanation:

Kristina wants to buy a flute that costs 240 . She has saved 20 each week for 3 weeks . How many more weeks does Kristina need to save money if she continues to save 20 each week

Answers

Answer:

9 more weeks

Explanation:

She already saved 20(3)=60

240=60+20(x)
X=9
She needs 9 more weeks

(x^2+1)(x-1)=0 help me pls

Answers

Answer:

x = ±i ,  x=1

Step-by-step explanation:

(x^2+1)(x-1)=0

Using the zero product property

x^2 +1 = 0   x-1= 0

x^2 = -1       x=1

Taking the square root of the equation on the left

sqrt(x^2) = sqrt(-1)

x = ±i   where  i is the imaginary number

We still have x=1 from the equation on the right

If P =
1 2
then, prove that P2 - 2P - 5 = 0, 1 = 0, where I and 0 are unit
3 1
matrix and null matrix of order 2 x 2 respectively.

Answers

Answer:

thanks for free ponits you dint gave it free but I theft I'm sorry

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