CMA Foundation · Fundamentals of Business Mathematics and Statistics · Probability
In a batch of 60 invoices at a Pune firm, 25 have errors in the GST amount, 20 have errors in the date, and 10 have errors in both. If one invoice is picked at random, what is the probability that it has an error in the GST amount or in the date?
The probability is 7/12. By the addition theorem, add the probabilities of a GST error (25/60) and a date error (20/60), then subtract the probability of both errors (10/60), giving 35/60, which simplifies to 7/12.
- A7/12Correct
- B3/4
- C1/2
- D11/12
Explanation
Use P(A or B) = P(A) + P(B) - P(A and B). That is 25/60 + 20/60 - 10/60 = 35/60 = 7/12. The option 3/4 equals 45/60 and comes from adding 25 and 20 without subtracting the overlap.
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