1. **State the problem:** We need to find the unit rate of children per group given 108 children divided into 4 groups. 2. **Formula:** The unit rate is found by dividing the total quantity by the number of groups. $$\text{Unit rate} = \frac{\text{Total children}}{\text{Number of groups}}$$ 3. **Apply the values:** $$\text{Unit rate} = \frac{108}{4}$$ 4. **Calculate:** $$\frac{108}{4} = 27$$ 5. **Interpretation:** There are 27 children in each group. **Final answer:** 27 children per group.