In Class XI of a certain school, there are 30 students in a Mathematics class and 20 students in Biolog class. Find the number of students which are in Mathematics class or in Biology class in the following cases:
(i) Two classes are conducted at the same time.
(ii) Two classes are condcuted at different time and 5 students study both the subject

Explanation

To solve the problem step by step, we will analyze both cases provided in the question.

### Given:
- Number of students in Mathematics class (N(M)) = 30
- Number of students in Biology class (N(B)) = 20

### Case (i): Two classes are conducted at the same time.

...