(i) We observe that the number of patients which take medical treatment in a hospital on a particular day less than 10 is 0. Similarly, less than 20 includes the number of patients which take medical treatment from 0-10 as well as the number of patients which take medical treatment from 10-20. So, the total of patients less than 20 is 0+60=60, we say that the cumulatives frequency of the class 10-20. Similarly for other class.
(ii) Also, we observe that all 300 patients which take medical treatment more than or equal to 10. Since, there are 60 patients which takes medical treatment in the interval 10-20 this means that there are 300-60=240 patients which take medical treatment more than or equal to 20. Continuing in the same manner.
