(i) The average marks obtained in an examination by two groups of students was found to be 75 and 85 respectively. Determine the ratio of students in the two groups, if the average mark for all students was 80.

(ii) On a certain examination, the average grade of all students in class A is 68.4 and all students in class B is 71.2. If the average of both classes combined is 70.0, what is the ratio of the number of students in class A to the number in class B?

(iii) The mean age of a combined group of men and women is 30 years. If the mean age of the group of men is 32 and that of the group of women is 27, find out the percentage of men and women in the group.