A student has to answer 10 out of 13 questions in an examination. The number of ways in which he can answer, if he must answer atleast three of the first five questions, is

Step-by-step solution

The possible cases are: Required number of ways = C 5 3 × C 8 7 + C 5 4 × C 8 6 + C 5 5 × C 8 5 = 5 × 4 2 × 8 + 5 × 8 × 7 2 + 1 × 8 × 7 × 6 3 × 2 = 80 + 140 + 56 = 276