The number of ways to distribute 10 identical red pens and 14 identical blue pens among four persons such that each person gets 6 pens, is ____.
Answer: 206
Solution
Let person receive red pens and blue pens. Then for each , and .
Since and , we need .
We need to count non-negative integer solutions to with .
Without upper bound: .
Subtract cases where some : If , substitute , giving solutions. By symmetry, 4 such cases.
Total: .
Since and , we need .
We need to count non-negative integer solutions to with .
Without upper bound: .
Subtract cases where some : If , substitute , giving solutions. By symmetry, 4 such cases.
Total: .
JEE Advanced · 2026 · 17 May 2026 · Paper 1 · Numerical answer