A ball is drawn from a box containing 10 red, 15 black, 5 green and 10 yellow balls. Find the probability that the ball is
(a) not green or yellow
My solutions:
P(G U Y) = P(G) + P(Y) = 1/8 + 1/4 = 3/8
1 - 3/8 = 5/8.
[I'm confused here: the formula is P(A U B) = P(A) + P(B) - P(A and B)... So I should find P(G and Y) too right...*blur*]
(b) not yellow
1 - 30/40 = 1 - 3/4 = 1/4
(c) red or black or green
My solutions:
10/40 + 15/40 + 5/40
= 1/4 + 3/8 + 1/8
= 2/8 + 3/8 + 1/8
= 6/8
= 3/4
[For this, are my workings correct? I know my answer is correct, if my workings are incorrect please do correct me..]
(d) not blue
My solutions:
[no idea]
Hmm I have to use this formula in some parts of the question right...
P(A U B) = P(A) + P(B) - P(A and B)
But I only use the P(A) + P(B)... eh.. I'm confused...
Tags: