A student is to answer 10 out of 13 questions in an examination such that he must choose at least 4 from the first five questions. The number of choices available to him is:
Solutions · 1
Official solution
Case 1 :
No of ways student can answer 10 questions = \[{}^5{C_4} \times {}^8{C_6}\] = 140
Case 2 :
No of ways student can answer 10 questions = \[{}^5{C_5} \times {}^8{C_5}\] = 56
\[\therefore\] Total ways = 140 + 56 = 196