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 <u>sum of all observations divided by the number of observations</u>.
In this problem:
- In the first 5 observations, total of 21 out of 25 points, hence the mean for these observations is
. - In the next n observations, mean of 1.
Hence, the mean is:

We want the mean to be of 0.9, thus:





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 brainly.com/question/25323941
Answer:
80
Step-by-step explanation:
<u><em>A = Area of First Rectangle </em></u>
<u><em>B = Area of Second Rectangle </em></u>
<u><em>w = Width</em></u>
<u></u>
12(w)=320+B (1st Equation)
8(w) = B (2nd Equation)
w=B/8 <em><u>(Plug this value of w into the first equation)</u></em>
12B/8 = 320 +B <u><em>(you get this)</em></u>
12B= 2560 + 8B <u><em>(Simplify)</em></u>
4B = 2560
B =640 <em><u>plug this value into the 2nd equation</u></em>
8(w) = 640
w = 80
<em>To Test This</em>
12x80 = 960
8x80 = 640
<h3>960 - 640 = 320
<u><em>Therefore the answer is correct the width is 80</em></u></h3>
<h3 />
Answer:
670
Step-by-step explanation:
(3*1+2)+(3*2+2)+........(3*20+2)=670