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meriva
3 years ago
5

A multiple choice exam has 20 questions. Each question has 3 possible answers; there is no partial credit. Only 1 answer out of

the 3 possible answers is correct; no questions are dependent on getting the correct answer for a previous question. The passing score for the exam is 60% or better. If you randomly guess the answer to each question, what is the probability that you will pass the test? Round your answer to three decimal places and report as a DECIMAL - example: 0.234
Mathematics
1 answer:
amid [387]3 years ago
6 0

Answer:To find out the theoretical probability of the case given, we need to make certain assumptions.

First, we'll assume that he'll attempt all of the questions, i.e he'll attempt all 10 questions.

Next assumption is that each option in each question is equally likely to be marked by the student.

This pretty much leads us to a binomial probability distribution.

Conditions are:

   Answers 10 questions.

   Each question has 4 options with only one correct answer and all other incorrect answers.

   Student is equally likely to pick any outcome in any given question.

   Hence, probability of choosing correct answer is 1/4 = 0.25. Probability of choosing incorrect answer is 1–1/4 = 3/4 = 0.75.

   The number of trials is 10.

   Total number of success is exactly 8 and failure is 2 amongst the 10 questions in any particular order.

Now, calculation is fairly simple.

Binomial probability distribution is such that…

P(8 correct ; 2 wrong)

= 10C8 × (0.25)^8 × (0.75)²

= 405/1048576 ≈ 3.862380981 × 10^-4 ≈ 0.000386

Step-by-step explanation:

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A snail can move 1/30 miles in 1/3 hour. How fast does a snail move in miles /hours
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Answer:             1/10 miles/hour

To find how fast a snail moves in miles per hour, we can find the unit rate using a proportion.

<h2>Unit Rate</h2>

The unit rate is the amount per one unit. In this problem, the unit is for one hour. One way to find the unit rate is by using a proportion.

<h2>Proportions</h2>

Proportions look like two fractions set equal to each other with a missing variable to solve.

<h3>State our variables</h3>

let <em>x</em> be the number of miles per hour

<h3>Write a proportion</h3>

The first fraction has a number for the numerator (top) and denominator (bottom), because the question gives us the information. The second fraction has a missing value, <em>x</em>, that we are solving for. We can write <em>x</em> in the numerator.

\displaystyle{\frac{\frac{1}{30}\ mi}{\frac{1}{3}\ hr} = \frac{x\ mi}{1\ hr}}

<h2>Solve</h2>

We can solve by finding the scale factor. The scale factor is the number we can multiply the numerator by to find <em>x</em>.

<h3>Find the scale factor</h3>

Start with the proportion.

\displaystyle{\frac{\frac{1}{30}\ mi}{\frac{1}{3}\ hr} = \frac{x\ mi}{1\ hr}}

To find the scale factor,

  1. Take the denominator from the fraction with a variable: 1\ hr
  2. Take the denominator from the fraction that has no variable:  \frac{1}{3}\ hr
  3. Divide step 1 by step 2 and solve:  1\ hr\ \div\ \frac{1}{3}\ hr = 3

Our scale factor is <u>3</u>.

<h3>Solve for x</h3>

We can find <em>x</em> by multiplying the numerator in the first fraction by the scale factor. This is because <em>x</em> is also in the numerator.

\displaystyle{\frac{\frac{1}{30}\ mi}{\frac{1}{3}\ hr} = \frac{(\frac{1}{30}\ mi)*3}{1\ hr}}

\displaystyle{\frac{\frac{1}{30}\ mi}{\frac{1}{3}\ hr} = \frac{\frac{3}{30}\ mi}{1\ hr}}

Simplify 3/30 by dividing the fraction by 3.

\displaystyle{\frac{\frac{1}{30}\ mi}{\frac{1}{3}\ hr} = \frac{\frac{1}{10}\ mi}{1\ hr}}

x = 1/10

∴ a snail moves 1/10 miles per hour.

Learn another way to solve proportions here: brainly.com/question/18437927

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