contestada

There are 10 boys and 13 girls in Mr. Benson's fourth-grade class and 12
boys and 11 girls in Mr. Johnson fourth-grade class. A picnic committee
of six people is selected at random from the total group of students in both
clasties.
(a) What is the probability that all the committee members are girls?
(b) What is the probability that the committee has three girls and three
boys?

Respuesta :

The number of ways 6 girls can be chosen from 24 girls is C(24, 6)
= 24! / (18! x 6!) = 134596
The number of ways 6 students can be chosen from 46 students is C(46, 6)
= 46! / (40! x 6!) = 9366819

a) P(6 girls are chosen) = 134596 / 9366819 = 0.01437 (4sf)

The number of ways 3 boys and 3 girls can be chosen is C(22, 3) x C(24, 3)
= [22! / (19! x 3!)] x [24! / (21! x 3!)] = 3116960

b) P(3 boys and 3 girls are chosen) = 3116960 / 9366819 = 0.3328 (4 sf)