The following chart shows the number of packages shipped(运输) per day for the last 100 days. 1. What is this chart called?( ) 2. What is the total number of frequencies?( ) 3. What is the class interval?( ) 4. What is the class frequency for the 10 up to 15 class?( ) 5. What is the relative frequency of the 10 up to 15 class?( )(结果写作百分数) 6. What is the midpoint of the 10 up to 15 class?( ) 7. On how many days were there 25 or more packages shipped?( ) 注:第2-7空的答案填数字,如 9,12,15%,12.5