(Q). 8 people are to be selected for a work from a group of 20 people such that exactly one from Mr. & Mrs. A is selected, similarly one from Mr. & Mrs. B and Mr. & Mrs. C and Mr. & Mrs. D is selected for the work. How many ways this can be done?
Solution:-
4 people from the group of Mr. & Mrs. A, B, C, D can be selected in 2×2×2×2 = 16 ways.
Now from remaining 20 – 2×4 = 12 people, 4 peoples can be selected in ¹²C₄ = 495 ways
∴ Total number of ways for selection
= 16×495
= 7920 ways Answer
