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on the last 5 quizzes, marco has earned a total of 21 out of 25 possible points. if he has a perfect score on the next several quizzes, exactly how many points will he need to bring up his average up to 90%

Sagot :

Using the mean concept, it is found that we will need 15 more points to bring up his average up to 90%.

The mean of a data-set is the sum of all observations divided by the number of observations.

In this problem:

  • In the first 5 observations, total of 21 out of 25 points, hence the mean for these observations is [tex]\frac{21}{25} = 0.84[/tex].
  • In the next n observations, mean of 1.

Hence, the mean is:

[tex]M = \frac{0.84(5) + n}{5 + n} = \frac{4.2 + n}{5 + n}[/tex]

We want the mean to be of 0.9, thus:

[tex]M = 0.9[/tex]

[tex]\frac{4.2 + n}{5 + n} = 0.9[/tex]

[tex]4.2 + n = 0.9n + 4.5[/tex]

[tex]0.1n = 0.3[/tex]

[tex]n = \frac{0.3}{0.1}[/tex]

[tex]n = 3[/tex]

3 more testes are need, each worth 5 points, hence, 15 more points are needed to bring up his average up to 90%.

A similar problem is given at https://brainly.com/question/25323941