Question 1191893
To find the greatest number of students the instructor can place in each group, we need to find the greatest common factor (GCF) of 28 and 20.

Here's how to find the GCF:

1. **List the factors of each number:**
   * Factors of 28: 1, 2, 4, 7, 14, 28
   * Factors of 20: 1, 2, 4, 5, 10, 20

2. **Identify the common factors:** 1, 2, 4

3. **The greatest common factor is 4.**

Therefore, the greatest number of students the instructor can place in each group is 4.