a teacher has 27 students in her class she asks the students to form as many groups of 4 as possible. how many students will not be in a group
There are 27 students in the class. The maximum number of groups of 4 is 6, since 6x4=24 and 7x4=28. (There cannot be 7 groups as there aren't enough students, but there are 6 groups.)
Once 6 groups have been formed, 24 students will belong to some group. (6x4=24). This leaves 3 students without a group (since 27-24=3.)
There will be 3 students who are not in a group of 4.