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# probability question watch

1. Can anyone help me with this?

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12 (a) A quality control officer inspects a large batch of electric light bulbs which are in packs of 8. He shooses a pack at random and tests all the bulbs to see if they are working. On this day 10% of the bulbs are faulty.

Find the probability that in the pack chosen

(i) none is faulty, [2]

(ii) two or more are faulty [5]

(b) If the officer finds no faulty bulbs, he accepts the whole batch. If he finds two or more faulty bulbs he rejects the whole batch. If he finds one faulty bulb then he chooses a seccond pack at random and accepts the whole batch only if this second pack has no faulty bulbs.

Find the probability that the whole batch is accepted. [5]
2. X - B(8,0.1)
i) P(X = 0)
ii) P(X >= 2) = 1 - P(X<=1)
b) P(X = 0) + P(X=1)*P(X=0)
3. (Original post by BCHL85)
X - B(8,0.1)
i) P(X = 0)
ii) P(X >= 2) = 1 - P(X<=1)
b) P(X = 0) + P(X=1)*P(X=0)
Could you explain what you did? Thanks.
4. Here are my workings

www.v-69.co.uk/stuff/maths1.JPG
www.v-69.co.uk/stuff/maths2.JPG

Sorry - am lazy and prefer to do maths by hand rather than typing

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