CMA Foundation · Fundamentals of Business Mathematics and Statistics · Probability
A box at a Pune stationery shop holds 6 blue, 4 black and 5 red pens. One pen is drawn at random. What is the probability that it is not black?
The probability of drawing a pen that is not black is 11/15. There are 15 pens in total and 4 are black, so the chance of black is 4/15, and the complement rule gives 1 minus 4/15, which equals 11/15.
- A4/15
- B11/15Correct
- C2/3
- D1/3
Explanation
Total pens = 6+4+5 = 15. Black pens = 4, so P(black) = 4/15. P(not black) = 1 - 4/15 = 11/15. Option 4/15 is the probability of black itself, which ignores the complement.
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