Question

A class consists of 10 boys and 8 girls.Three students are selected at random.Find the probability that the selected row has

Answer 1

Step 1:

(a)No of boys in the class=10

No of students selected =3

Samle space n(s)=18C3

No of boy selected is that all are boys n(A)=10C3

∴ the probability that all are boys P(A)=n(A)n(S)

⇒10C318C3

Step 2:

(b) No of girls in the class =8

No of students selected=3

No of girl selected is that all are girlss n(B)=8C3

∴ the probability that all are girls P(B)=n(B)n(S)

⇒8C318C3

Step 3:

(c) The probability that 2 boys and 1 girl is selected to be n(C)n(S)

⇒10C3×8C318C3