In the fifth grade, 47 students took part in a math contest, and their scores were all integers. The full score was 100. It is known that three students scored below 60, while others scored between 75 and 95. Q: How many students have the same grades at least?

Answer and analysis:

Analysis 120÷2=60, 90÷2=45, the distance between every two trees is their common divisor. (120,60,90,45) =15, a * * key: (120+90)×2÷ 15=28 (tree).