Competition 73174

There are 10 students in the class, of which 8 are girls and two are boys. We want to select three for the competition. What is the probability that they will be:
a) 2 girls and 1 boy
b) 1 girl and 2 boys
c) 3 girls
d) 3 boys
e) at least 2 girls

Correct answer:

a =  0.4667
b =  0.0667
c =  0.4667
d =  0.025
e =  0.9333

Step-by-step explanation:

C2(8)=(28)=2!(82)!8!=2187=28 C1(2)=(12)=1!(21)!2!=12=2 C3(10)=(310)=3!(103)!10!=3211098=120 n1=8 n2=2  a=(3n1+n2)(2n1) (1n2)=(38+2)28 2=157=0.4667
C1(8)=(18)=1!(81)!8!=18=8 C2(2)=(22)=2!(22)!2!=11=1 b=(3n1+n2)(1n1) (2n2)=(38+2)8 1=151=0.0667
C3(8)=(38)=3!(83)!8!=321876=56  c=(3n1+n2)(3n1)=(38+2)56=157=0.4667
C2(3)=(23)=2!(32)!3!=13=3 d=(3n1+n2)(3n2)=(38+2)(32)=401=0.025
e=(3n1+n2)(2n1) (1n2)+(3n1)=(38+2)28 2+56=1514=0.9333



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