9. Xiao Ming participated in four Chinese tests, with an average score of 68. He wants to increase his average score to over 70 after the next Chinese test, so what is the minimum score he needs to achieve in the next test?
9. The fifth test score must be at least 78 points
9.【Solution】 $70 \times 5-68 \times 4=78$ (points) 【Another Solution】 $70+4 \times(70-68)=78$ (points)