2/7
4 days is 4/7 of a week
It is 4/7 of a week
Three days is 3/7 of a week, which is a bit less than half.
7/7
A fraction requires two numbers. 21 days as a fraction of what? A month, a year, a century?
2/7
Each day is 1/7 of a week (because there are 7 days per week).
4 days is 4/7 of a week
It is 5/7, because there are 7 days in a week.
2/7 of a week would be two days since a week is seven days, two 'parts' of a week would be two days.
It is 4/7 of a week
6/7
One day is 1/7 of a week, since a week consists of seven days. Therefore, if you take one day and divide it by the total number of days in a week, you get the fraction 1/7.
3/7There are 7 days in one week. 3 out of 7 days = 3/7
Three days is 3/7 of a week, which is a bit less than half.
Both are acceptable.
7/7