Question
there are 6 white balls and 4 black balls.i takeout 2 balls at random,one at a time,without replacement.What is the probability that the second ball i take is black
Answers
MathMate
Make a probability tree.
If the first one is white
P(W)=6/10
P(WB)=(6/10)(4/9)=24/90
If the first one is black:
P(B)=4/10
P(BB)=(4/10)(3/9)=12/90
P(XB)=P(WB)+P(BB)=24/90+12/90=36/90=2/5
If the first one is white
P(W)=6/10
P(WB)=(6/10)(4/9)=24/90
If the first one is black:
P(B)=4/10
P(BB)=(4/10)(3/9)=12/90
P(XB)=P(WB)+P(BB)=24/90+12/90=36/90=2/5