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Oliga [24]
3 years ago
7

Alexandra scored 40 on an exam, receiving 3 points for each right answer and losing 1 point for each wrong answer. Had 4 points

been given for each right answer and 2 points deducted for each wrong answer, Alexandra would have scored 50. How many questions were on the exam
Mathematics
1 answer:
vagabundo [1.1K]3 years ago
3 0

Answer: there were 20 questions in the exam.

Step-by-step explanation:

Let x represent the number of right answers.

Let y represent the number of wrong answers.

Alexandra scored 40 on an exam, receiving 3 points for each right answer and losing 1 point for each wrong answer. It means that

3x - y = 40- - - - - - - - - - 1

Had 4 points been given for each right answer and 2 points deducted for each wrong answer, Alexandra would have scored 50. It means that

4x - 2y = 50- - - - - - - - - - -2

Multiplying equation 1 by 2 and equation 2 by 1, it becomes

6x - 2y = 80

4x - 2y = 50

Subtracting both equations, it becomes

2x = 30

x = 30/2

x = 15

Substituting x = 15 into equation 1, it becomes

3 × 15 - y = 40

45 - y = 40

y = 45 - 40

y = 5

The number of questions in the exam is

x + y = 15 + 5 = 20

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The distribution of the number of viewers for the American Idol television show follows a normal distribution with a mean of 26
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Answer:

Probability that next week's show will have between 30 and 37 million viewers is 0.2248.

Step-by-step explanation:

We are given that the distribution of the number of viewers for the American Idol television show follows a normal distribution with a mean of 26 million with a standard deviation of 8 million.

<em>Let X = number of viewers for the American Idol television show</em>

So, X ~ N(\mu=26,\sigma^{2}=8^{2})

Now, the z score probability distribution is given by;

          Z = \frac{X-\mu}{\sigma} ~ N(0,1)

where, \mu = population mean = 26 million

            \sigma = standard deviation = 8 million

So, probability that next week's show will have between 30 and 37 million viewers is given by = P(30 < X < 37) = P(X < 37) - P(X \leq 30)

    P(X < 37) = P( \frac{X-\mu}{\sigma} < \frac{37-26}{8} ) = P(Z < 1.38) = 0.91621

    P(X \leq 30) = P( \frac{X-\mu}{\sigma} \leq \frac{30-26}{8} ) = P(Z \leq 0.50) = 0.69146

<em>Therefore, P(30 < X < 37) = 0.91621 - 0.69146 = 0.2248</em>

Hence, probability that next week's show will have between 30 and 37 million viewers is 0.2248.

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3 years ago
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1782/3 = and why the answer
never [62]

Answer:

594

Step-by-step explanation:

1782/3 = 594.

To if the answer is correct, you do this:

594 × 3 = 1782.

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Step-by-step explanation:

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Step-by-step explanation:

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Hint:

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