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Andre45 [30]
3 years ago
8

What is the probability of randomly guessing at least 8 out of 10 questions correct on a true-or-false quiz?

Mathematics
1 answer:
Kay [80]3 years ago
3 0
P( at least 8 correct ) = 
<span>........P( 8 ) + P( 9 ) + P( 10 ) = </span>
<span>........(10 C 8).5^10 + (10 C 9).5^10 + (10 C 10).5^10 = ........56*.5^10 = 0.0546875 </span>

<span>Note: Let C denote correct and I denote incorrect. Suppose that guessing results in 8 correct and 2 incorrect answers. One possible outcome is CCCCCCCCII, for example. We can think of the number of ways of getting exactly 8 correct to be the same as the number of ways of selecting 8 spots for the correct answers times the number of ways of selecting two spots for the remaining two answers. There are (10 C 8) ways to select the positions for the correct answers and precisely one way to select the remaining two positions for the incorrect answers. Therefore, there are there are 10 C 8 = 45 ways to get 8 correct. Similarly, there are 10 C 9 = 10 ways to get 9 correct, and 10 C 10 = 1 way to get all 10 correct.</span>
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Here is a diagram and its corresponding equation. Find the solution to the equation and explain your reasoning 38 x+7 x+7 x+7 x+
QveST [7]

Answer:

x = (-158)/87

Step-by-step explanation:

Solve for x:

38 x + 7 x + 7 x + 7 x + 7×4 (x + 7) = 38

Hint: | Multiply 7 and 4 together.

7×4 = 28:

38 x + 7 x + 7 x + 7 x + 28 (x + 7) = 38

Hint: | Group like terms in 38 x + 7 x + 7 x + 7 x + 28 (x + 7).

Grouping like terms, 38 x + 7 x + 7 x + 7 x + 28 (x + 7) = 28 (x + 7) + (38 x + 7 x + 7 x + 7 x):

28 (x + 7) + (38 x + 7 x + 7 x + 7 x) = 38

Hint: | Add like terms in 38 x + 7 x + 7 x + 7 x.

38 x + 7 x + 7 x + 7 x = 59 x:

28 (x + 7) + 59 x = 38

Hint: | Distribute 28 over x + 7.

28 (x + 7) = 28 x + 196:

28 x + 196 + 59 x = 38

Hint: | Add like terms in 59 x + 28 x + 196.

28 x + 59 x = 87 x:

87 x + 196 = 38

Hint: | Isolate terms with x to the left hand side.

Subtract 196 from both sides:

87 x + (196 - 196) = 38 - 196

Hint: | Look for the difference of two identical terms.

196 - 196 = 0:

87 x = 38 - 196

Hint: | Evaluate 38 - 196.

38 - 196 = -158:

87 x = -158

Hint: | Divide both sides by a constant to simplify the equation.

Divide both sides of 87 x = -158 by 87:

(87 x)/87 = (-158)/87

Hint: | Any nonzero number divided by itself is one.

87/87 = 1:

Answer: x = (-158)/87

5 0
3 years ago
A right triangle has a hypotenuse C=12cm and a an angle A= 30°. find the length of side a, witch is opposite angle A
Alisiya [41]
Use the sin identity to find that side.  Sin(30) = a/12...12 sin(30) = a, and a = 6
7 0
4 years ago
A portion of the Quadratic Formula proof is shown. Fill in the missing statement.
Zielflug [23.3K]

Answer:

Option A.

Step-by-step explanation:

we have

x+\frac{b}{2a} =\pm\sqrt{\frac{b^2-4ac}{4a^2}}

Simplify the right side of the equation

we know that

\pm\sqrt{\frac{b^2-4ac}{4a^2}}=\pm\frac{\sqrt{b^2-4ac}}{\sqrt{4a^2}}=\pm\frac{\sqrt{b^2-4ac}}{2a}

so

The expression is

x+\frac{b}{2a}=\pm\frac{\sqrt{b^2-4ac}}{2a}

therefore

x plus b over 2 times a equals plus or minus the square root of b squared minus 4 times a times c, all over 2 times a

4 0
3 years ago
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ohaa [14]

Answer:

B. (6, 8)

Step-by-step explanation:

To figure this out, you can plug in the coordinates to see if you get matching answers. Since you believe answer "B," is correct, we can check:

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8 - 8 = -3(6 - 6)

0 = -3(0)

0 = 0

<u>Since the answers match, that makes answer "B," correct.</u>

4 0
3 years ago
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laila [671]

Answer:

$12.60 is the new price!

Step-by-step explanation:

20 x 0.7 = 14

14 x 0.9 = 12.6

Hope this helped!

4 0
3 years ago
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