Question

a student has to answer 10 questions, choosing at least 4 from each of part A and part B. If there are 6 questions in part A and 7 in part B, in how many ways can the student choose 10 questions.

Answer 1

Since the problem is related to selection, we will choose combination.

Since atleast 4 Qs have to be selected from both A and B, therefore:

Next what about the remaining 2 questions.

1 from A and 1 from B

2 from A

2 from B

6C4*7C6 + 6C6*7C4 + 6C5*7C5