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
Hi love...
The correct answer after solving for d is D=78. That’s a quick answer, but I can give you steps on how to solve.
1. Simplify both sides of the equation
2. Isolate the variable
3. Simplify
Then you’d have the answer!
Please let me know if you need further assistance! Have a jolly evening.
~Brooke❤️