A question paper has two parts P and Q, each containing 10 questions. If a student needs to choose 8 from part P and 4 from part Q, in how many ways can he do that?
None of these
6020
1200
9450
Explanation:
Number of ways to choose 8 questions from part P = 10C8
Number of ways to choose 4 questions from part Q = 10C4
Total number of ways
= 10C8 × 10C4
= 10C2 × 10C4 [nCr = nC(n-r)]
=$\left(\dfrac{10 \times 9}{2 \times 1}\right) \left(\dfrac{10 \times 9 \times 8 \times 7}{4 \times 3 \times 2 \times 1}\right)$=45×210=9450