1. **State the problem:** A class of 25 students has an average score of 73 on a Physics test. A new student joins and scores 77. We need to find the new average score. 2. **Formula for average:** The average score is given by $$\text{Average} = \frac{\text{Sum of all scores}}{\text{Number of students}}$$ 3. **Calculate the total sum of scores before the new student:** $$\text{Sum}_{\text{old}} = 25 \times 73 = 1825$$ 4. **Add the new student's score to the total sum:** $$\text{Sum}_{\text{new}} = 1825 + 77 = 1902$$ 5. **Calculate the new number of students:** $$\text{Number}_{\text{new}} = 25 + 1 = 26$$ 6. **Calculate the new average:** $$\text{Average}_{\text{new}} = \frac{1902}{26}$$ 7. **Simplify the fraction:** $$\text{Average}_{\text{new}} = \frac{\cancel{1902}}{\cancel{26}} = 73.1538...$$ 8. **Round to one decimal place:** $$\text{Average}_{\text{new}} \approx 73.2$$ **Final answer:** The new average score for the class is **73.2**.