What is the working out you have done?
3. A bag contains 10 balls, 4 are red and 6 are yellow. Three balls are drawn without replacement. What is the probability of drawing at least two red balls?
4. A town has two fire engines operating independently. The probability that a specific fire engine is available when need is 0.95. What is the probability that neither is available when needed? What is the probability that a fire engine is available when needed?
OK could someone help out a little bit my brain is failing to work, I have done some working out but none of it seems to make sense and it seems easy. Don't know what's going on up there.
Hello, djmccabie!
3. A bag contains 10 balls, 4 are red and 6 are yellow.
Three balls are drawn without replacement.
What is the probability of drawing at least two red balls?
We draw 3 balls from 10 balls.
There are: . possible outcomes.
We want 3 Red balls, or 2 Red and 1 Yellow.
. . 3R: . ways.
. . 2R, 1Y: . ways.
Hence, there are: . ways to get at least 2 red balls.
Therefore: .
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You could have solved it taking baby steps . . .
There are four ways to get at least 2 red balls: .RRR, RRY, RYR, YRR.
. .
Therefore: .