WINTER HOLIDAY HOMEWORK [Ch.20 Q2]
Level
2
There are 7 adults, 5 children and 4 babies. In randomly choosing 12 people, what is the probability that 4 adults, 4 children and 4 babies are chosen?
A: (7P4 x 5P4 x 4P4)÷16C4
B: (7C4 x 5C4 x 4C4)÷16C12
C: (7C4 + 5C4 +4C4)÷16C12
C
None of them are right
A
B
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1 solution
probability= number of desired÷ total possible number
we need to choose 4 adults from 7 adults, it's a combination question. So we should write it as 7C4.
Then use 7C4 to multiplied by 5C4 and 4C4.
total possible number is 16C12. 16 is come from (7+5+4), we need to choose (4+4+4) people from total 16 people.