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3 years ago

Write each set of numbers in set-builder and interval notation X>50

Mathematics

1 answer:

KiRa [710]3 years ago

7 0

Answer:

$\{x\ E\ Z\ |\ x > 50\}$ ---- Set Builder

(50, ∞) ---- Interval Notation

Step-by-step explanation:

Given

x > 50

Required

Write as a

- Set builder

- Interval notation

As Set Builder:

x > 50 means that x is an integer and x is greater than 50.

In set builder notation, integers are represented with z.

So, the above can be represented as:

$\{x\ E\ Z\ |\ x > 50\}$

This translates to:

x is a member of the set of integers such that x is greater than 50

As Interval Notation:

In interval notation, we make use of brackets to represent the intervals.

In this case > is represented by (a,b)

Where a and b are the intervals of the notation

Since x > 50, then a = 50 and b = ∞ because we only know the starting point and not the end point.

<em>Hence: x > 50 in interval notation is (50, ∞)</em>

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there are 9 boys in a class of 14 students. a)what is the ratio of boys to girls. b) what is the ratio of girls to all students

ElenaW [278]

Answer:

a). 9 to 5

b). 5 to 14

Step-by-step explanation:

If there are 9 boys then there are 5 girls because 14 - 9 = 5.

So, there are 5 girls of 14 students in the class.

4 0

3 years ago

Judy worked 8 hours and Ben worked 10 hours. Their combined pay was $80. When Judy worked 9 hours and Ben worked 5 hours, their

pav-90 [236]

Answer:

Judy = $5/hr

Ben = $4/hr

Step-by-step explanation:

Judy's hours at work - x

Ben's hours at work - y

8x + 10y = 80

9x + 5y = 65

Given these two equations above, we get:

10y = 80 - 8x, which means y = 8 - 0.8x.

Substitute y in the second equation with 8 - 0.8x, so we have:

9x + 5 (8 - 0.8x) = 65

9x + 40 - 4x = 65

5x = 25

x = 5

Come back to the first equation, substitute x:

8*5 + 10y = 80

10y = 80 - 40

y = 4

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3 years ago

A market research team compiled the following discrete probability distribution, where X represents the number of automobiles ow

rodikova [14]

Answer:

The standard deviation of X is 0.7

Step-by-step explanation:

We are given the following distribution:

x: 0 1 2 3

P(x): 0.3 0.5 0.2 0.4

We have to find the standard deviation of X.

Formula:

$E(x) = \displaystyle\sum x_iP(x_i)\\\\E(x) =0(0.3) + 1(0.5) + 2(0.2) + 3(0.4)\\\\E(x) = 2.1\\\\E(x^2) = \displaystyle\sum x_i^2P(x_i)\\\\E(x^2) =0(0.3) + 1(0.5) + 4(0.2) + 9(0.4)\\\\E(x^2) = 4.9\\\\Var(x) = E(x^2) - (E(x))^2 = 4.9-(2.1)^2 = 0.49\\\\\sigma(x) = \sqrt{Var(x)} =\sqrt{0.49} = 0.7$

Thus, the standard deviation of X is 0.7

6 0

3 years ago

An olympic sprinter can run 56 yards in 8 seconds. At the same rate, how long (in seconds) would it take the sprinter to run 81

aniked [119]

Answer:

20,365.7 seconds

Step-by-step explanation:

First, we need to know how to convert yards to miles, as the question is in miles. We know that 1 mile is equivalent to 1760 yards. So we have:

1 mi = 1760 yards

If we multiply both sides by 81:

81 mi = 142,560‬ yards

And we know that the sprinter needs 8 second to run 56 yards:

8 s = 56 yards

If we divide both sides by 56 we get the time he needs for 1 yard:

8/56 s = 56/56 yards

1/7 s = 1 yard

So, takes him 1/7 seconds to run one yard. At this rate he runs 142,560 yards in:

(1/7) * 142,560 = 20,365.7

So, he needs 20,365.7 seconds to run 81 miles (142,560 yards)

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3 years ago

the volume v of a right circular cylinder of radius r and heigh h is V = pi r^2 h 1. how is dV/dt related to dr/dt if h is const

laiz [17]

In general, the volume

$V=\pi r^2h$

has total derivative

$\dfrac{\mathrm dV}{\mathrm dt}=\pi\left(2rh\dfrac{\mathrm dr}{\mathrm dt}+r^2\dfrac{\mathrm dh}{\mathrm dt}\right)$

If the cylinder's height is kept constant, then $\dfrac{\mathrm dh}{\mathrm dt}=0$ and we have

$\dfrac{\mathrm dV}{\mathrm dt}=2\pi rh\dfrac{\mathrm dt}{\mathrm dt}$

which is to say, $\dfrac{\mathrm dV}{\mathrm dt}$ and $\dfrac{\mathrm dr}{\mathrm dt}$ are directly proportional by a factor equivalent to the lateral surface area of the cylinder ( $2\pi r h$ ).

Meanwhile, if the cylinder's radius is kept fixed, then

$\dfrac{\mathrm dV}{\mathrm dt}=\pi r^2\dfrac{\mathrm dh}{\mathrm dt}$

since $\dfrac{\mathrm dr}{\mathrm dt}=0$ . In other words, $\dfrac{\mathrm dV}{\mathrm dt}$ and $\dfrac{\mathrm dh}{\mathrm dt}$ are directly proportional by a factor of the surface area of the cylinder's circular face ( $\pi r^2$ ).

Finally, the general case ( $r$ and $h$ not constant), you can see from the total derivative that $\dfrac{\mathrm dV}{\mathrm dt}$ is affected by both $\dfrac{\mathrm dh}{\mathrm dt}$ and $\dfrac{\mathrm dr}{\mathrm dt}$ in combination.

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3 years ago