Statistics question- Please let me know if this is correct

Question

Students at the high school are allowed to sign up for one English class each year. The numbers of students signing up for various English classes for the next school year are given below-

English 1 English 2 English 3 English IV Total

10th 60 165 20 15 260

11th 35 40 115 10 200

12th 10 25 90 145 270

total 105 230 225 170 730

What is the probability that an 11th-grader will take either English II or English III?

I am not sure if I use total number of students 730 or total number of 11th graders (200).

Answer 1

You will use 200 for this problem since this is asking for 11th graders, not all students.

P(Eng 2 or Eng 3) = P(Eng 2) + P(Eng 3) - P(Eng 2 and Eng 3)

= (40/200) + (115/200) - 0

= 155/200

= 0.775

The probability that an 11^th grader will take either English 2 or English 3 is 0.775.

Note: Each student is only allowed to take one English class. No student can do more than one English class, which explains that one of the probabilities from above is mutually exclusive.