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Mashcka [7]
3 years ago
15

A grading scale is set up for 1000 students' test scores. It assumes the

Mathematics
1 answer:
astra-53 [7]3 years ago
7 0

Answer:

464 students will score between 48 and 75. Using the z-distribution, we measure how many standard deviations each score is from the mean, then find the p-value associated with each score to find the proportion, and from the proportion, we find how many out of 1000.

Step-by-step explanation:

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the z-score of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

It assumes the scores are normally distributed with a mean score of 75 and a standard deviation of 15.

This means that \mu = 75, \sigma = 15

How many students will score between 48 and 75?

First we find the proportion, which is the pvalue of Z when X = 75 subtracted by the pvalue of Z when X = 48. So

X = 75

Z = \frac{X - \mu}{\sigma}

Z = \frac{75 - 75}{15}

Z = 0

Z = 0 has a p-value of 0.5

X = 48

Z = \frac{X - \mu}{\sigma}

Z = \frac{48 - 75}{15}

Z = -1.8

Z = -1.8 has a p-value of 0.0359

1 - 0.0359 = 0.4641

Out of 1000:

0.4641*1000 = 464

464 students will score between 48 and 75. Using the z-distribution, we measure how many standard deviations each score is from the mean, then find the p-value associated with each score to find the proportion, and from the proportion, we find how many out of 1000.

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Step-by-step explanation:

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A trapezoid has bases of lengths 13 cm and 17 cm. The
Vedmedyk [2.9K]

Answer:

135 cm²

Step-by-step explanation:

The area (A) of a trapezoid is calculated as

A = \frac{1}{2} h(a + b)

where h is the height and a, b the parallel bases

Here h = 9, a = 13 and b = 17 , thus

A = \frac{1}{2} × 9 × (13 + 17)

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3 years ago
In a company, 37‰ of the 1500 employees are female. how many are male?
Mashcka [7]

Answer:

945 males

Step-by-step explanation:

1500*37/100= 555 female

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A mobile company charges a fixed rate of x cents per minute for the first 120 minutes of talk time and another rate of y cents p
patriot [66]

Answer:

$21.2

Step-by-step explanation:

From the problem given, we express them as algebra so that we can easily solve;

    the total charge on a call greater than 120min is given as;

   120x + y(n - 120) = total cost of call

where n is the number of minutes which is greater than 120;

  •   Ethan paid $26.80  for 175 mins

  n = 175min here;

      120x + y(175 - 120) = 26.80

       120x + 55y = 26.80 ----- (I)

  • $32.40 for 210 minutes

      n = 210min

       120x + y(210 - 120) = 32.4

       120x + 90y = 32.4 ----- (II)

Now let us solve both equations for y and x;

      120x + 55y = 26.80 ----- (I)

     120x + 90y = 32.4 ----- (II)

subtract the two equations;

             90y - 55y = 32.4 - 26.8

                  35y = 5.6

                       y = \frac{5.6}{35}  = 0.16cents

then x;

       120x = 26.8 - 55y from equation I

       120x = 26.8 - 55(0.16)

       120x = 18

            x = \frac{18}{120}  = 0.15cents

Find the cost of 140min of talk time;

  n =140min;

      =  120(0.15) + 0.16(140 - 120)

      = 18 + 0.16(20)

      = 18 + 3.2

      = $21.2

4 0
3 years ago
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