Answer: Fourt option: 3/20
Solution:
Probability that both balls are blue?
Event: Ball drawn from Urn I is blue: A
Event: Ball drawn from Urn II is blue: B
Probability that both balls are blue=Probability that ball drawn from Urn I is blue and ball drawn from Urn II is blue
Probability that both balls are blue = P(A ∩ B)
These events are independent, then:
P(A ∩ B)=P(A) P(B)
P(A)=(Number of blue balls in Urn I)/(Total number of balls in Urn I)
Total number of balls in Urn I=4 green +6 blue=10
P(A)=6/10
Simplifying the fraction: Dividing the numerator and denominator by 2:
P(A)=(6/2)/(10/2)
P(A)=3/5
P(B)=(Number of blue balls in Urn I))/(Total number of balls in Urn II)
Total number of balls in Urn II=6 green +2 blue=8
P(B)=2/8
Simplifying the fraction: Dividing the numerator and denominator by 2:
P(B)=(2/2)/(8/2)
P(B)=1/4
Then:
P(A ∩ B)=P(A) P(B)=(3/5)(1/4)=[(3)(1)] / [(5)(4)]
P(A ∩ B)=3/20