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liubo4ka [24]
3 years ago
6

A multiple-choice test has 30 questions and each one has five possible answers, of which only one is correct. If all answers wer

e guesses, find the probability of getting exactly four correct answers.
Mathematics
1 answer:
kumpel [21]3 years ago
5 0

Answer: the probability is 0.13

Step-by-step explanation:

First, each question has 5 options and only one is correct.

Then, selecting at random, the probability of getting a correct answer is equal to:

p = 1/5 = 0.20 (and the probability of getting it incorrect is p = 4/5 = 0.80)

Now, if out of 30 questions, we got 4 correct and 26 incorrect, the probability for a given combination is;

p = (0.20^4)*(0.80^26)

But we also need to multiply this by the total number of combinations.

This is we have 30 questions in total, and we can select 4 of them that will be the correct ones.

Now, if we have N objects in total, the number of different combinations of K elements out of those N elements is

C = \frac{N!}{(N-K)!*K!}

In this case, N = 30 and K = 4.

C = \frac{30!}{(30 -4)!*4!} = \frac{30*29*28*27}{4*3*2}  = 27,405

Then the probability of getting exactly 4 correct answers is:

P = (0.20^4)*(0.80^26)*27,405 = 0.13

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How do I apply the distributive property to create an equivalent expression for 4(6 + 6y)
tia_tia [17]

Answer:

24y+24

Step-by-step explanation:

You multiply the number on the outside of the parenthesis with both the numbers on the inside of the parenthesis. The + stays the same.

4*6y=24y

4*6=24

Hope this helps!

4 0
2 years ago
Solve the following equations <br>x-1=6/x​
Whitepunk [10]

Answer:

or,x2-x=6

or,x2-x-6=0

or,x2-3x+2x-6=0

or,x(x-3)+2(x-3)=0

or,(x-3)(x+2)=0

so either x=3

or x=-2

3 0
3 years ago
Each course at a community college is worth 1 or 2 credits. A group of students is taking a total of 16 courses that are worth a
Anuta_ua [19.1K]

Answer:

They  are taking 12 2 credit courses

The are taking 4  1 credit courses

Step-by-step explanation:

x = 1 credit courses

y = 2 credit courses

The number of courses is 16

x+y = 16

The number of credits is 28 so multiply the course by the number of credits

1x+2y=28

Subtract the first equation from the second equation

x+2y =28

-x-y=-16

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

y = 12

They  are taking 12 2 credit courses

We still need to find the 1 credit courses

x+y = 16

x+12= 16

Subtract 12 from each side

x-12-12 = 16-12

x =4

The are taking 4  1 credit courses

6 0
2 years ago
Which number should.be added to the data so that the range of the data is 31? 54,72,64,57
Sergio039 [100]

Answer:  41 or 85

<u>Step-by-step explanation:</u>

Range is the difference between the largest number and the smallest number.

The largest number is 72.  72 - 31 = 41

The smallest number is 54.  54 + 31 = 85

Adding either ONE of those numbers will result in a range of 31.

3 0
3 years ago
Consider the quadratic function f(x) = –2x2 + 4x – 2. Find the y-intercept and the equation of the axis of symmetry.
RoseWind [281]

Answer:

The y-intercept is -2

The equation of the axis of symmetry is x = 1 ⇒ 3rd answer

Step-by-step explanation:

* Lets revise the general form of the quadratic function

- The general form of the quadratic function is f(x) = ax² + bx + c,

 where a, b , c are constant

# a is the coefficient of x²

# b is the coefficient of x

# c is the y-intercept

- The meaning of y-intercept is the graph of the function intersects

 the y-axis at point (0 , c)

- The axis of symmetry of the function is a vertical line

  (parallel to the y-axis) and passing through the vertex of the curve

- We can find the vertex (h , k) of the curve from a and b, where

 h is the x-coordinate of the vertex and k is the y-coordinate of it

# h = -b/a and k = f(h)

- The equation of any vertical line is x = constant

- The axis of symmetry of the quadratic function passing through

  the vertex then its equation is x = h

* Now lets solve the problem

∵ f(x) = -2x² + 4x - 2

∴ a = -2 , b = 4 , c = -2

∵ The y-intercept is c

∴ The y-intercept is -2

∵ h = -b/2a

∴ h = -4/2(-2) = -4/-4 = 1

∴ The equation of the axis of symmetry is x = 1

4 0
2 years ago
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