Respuesta :
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
