https://v.cx/2010/04/feynman-brazil-education

> Then I held up the elementary physics textbook they were using.

> There are no experimental results mentioned anywhere in this book, except in one place where there is a ball, rolling down an inclined plane, in which it says how far the ball got after one second, two seconds, three seconds, and so on.

> The numbers have ‘errors’ in them – that is, if you look at them, you think you’re looking at experimental results, because the numbers are a little above, or a little below, the theoretical values. The book even talks about having to correct the experimental errors – very fine.

> The trouble is, when you calculate the value of the acceleration constant from these values, you get the right answer.

> But a ball rolling down an inclined plane, if it is actually done, has an inertia to get it to turn, and will, if you do the experiment, produce five-sevenths of the right answer, because of the extra energy needed to go into the rotation of the ball.

> Therefore this single example of experimental ‘results’ is obtained from a fake experiment.

> Nobody had rolled such a ball, or they would never have gotten those results!

Reading your post, I now realize education is dysfunctional in the entire world, not just in my country. Small comfort.

Interesting. If that is correct and you take OPs value, 6.8 / 5 * 7 = 9.5 which is pretty damn close. So his failed grade was for the only non-cheated result?