First, read the English article below.

Let's use x to represent the percentage. The formula to use when converting a percentage into a GPA (with a scale of 4.0) is (x/20) - 1 = GPA. Let's say you have an 89% in Geology. Just plug it into the formula to get the following:  89/20 - 1 = 4.45 - 1 = 3.45. The GPA equivalent of 89% is 3.45. The process will be the same even if your percentage is higher than 100%. Let's say you got a whopping 108% in Algebra. Here's what happens when you plug it in:  108/20 - 1 = 5.4 - 1 = 4.4 The GPA equivalent of 108% is 4.4. This may be useful depending on what you are calculating your GPA for. If you are calculating one grade at a time to see how they will add up for your high school GPA, then you may not have to follow this exact formula because all grades will fall within a range anyway. For example, if your grade falls within the range of 83-86, then depending on your high school, then you will have a B, or a 3.0, whether it falls on the higher or lower part of the range or not. Check out your school's GPA system to figure out how to do this; some high schools have a slightly different range for what makes an A- vs. an A, a B vs. a B+, and so on. 

Now, please write a short abstract for it in Vietnamese. Abstract:
Biết công thức quy đổi một tỷ lệ phần trăm sang điểm GPA thang 4.0. Chèn phần trăm vào công thức và tính. Dùng công thức tương tự nếu tỷ lệ phần trăm cao hơn 100%. Cân nhắc sử dụng thang điểm.