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3 years ago

N a second grade class containing 12 girls and 11 boys, 2 students are selected at random to give out the math papers. what is t

he probability that both are girls?

Mathematics

1 answer:

ira [324]3 years ago

7 0

$\displaystyle
|\Omega|=\binom{23}{2}=\dfrac{23!}{2!21!}=\dfrac{22\cdot23}{2}=253\\
|A|=\binom{12}{2}=\dfrac{12!}{2!10!}=\dfrac{11\cdot12}{2}=66\\\\
P(A)=\dfrac{66}{253}=\dfrac{6}{23}$

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See the attached figure

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we know that

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