JEE MAIN - Mathematics (2003 - No. 43)
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
346
140
196
280
Spiegazione
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