10 out of 21 means 11 wrong answers
Scoring 10 out of 21 is the same as getting 11 wrong out of 21. Both describe one result: 10 correct answers on a 21-question test. Whether your teacher counts up from correct answers or down from wrong ones, the percentage is identical.
How the 10 out of 21 percentage is calculated
The percentage comes from one division: 10 Γ· 21 Γ 100 = 47.62%. Every question on a 21-question test is worth 4.76% of the total score.
Why 47.62% is an F on the standard scale
The standard 10-point scale puts an F below 60%, so a 47.62% test earns an F. That converts to a 0.0 on the 4.0 GPA scale.
How many can you miss on a 21-question test?
Every letter grade on a 21-question test has a maximum number of wrong answers.
Letter grade cutoffs for a 21-question test
- A β at least 19 correct (miss no more than 2 questions)
- B β at least 17 correct (miss no more than 4 questions)
- C β at least 15 correct (miss no more than 6 questions)
- D β at least 13 correct (miss no more than 8 questions)
Anything at or below 12 correct falls under 60% and is an F on this scale. Your own class may round differently or use a curve, so treat these cutoffs as the common default rather than a rule.