Class 9 Probability of an Event — practice questions with answers
Statistics · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.
1. In Class 9 probability, the empirical probability of an event E is given by which formula?
A(Number of trials in which E happened) / (Total number of trials)
B(Total number of trials) / (Number of trials in which E happened)
C(Number of trials in which E happened) x (Total number of trials)
D(Number of favourable outcomes) / (Number of unfavourable outcomes)
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Answer: A) (Number of trials in which E happened) / (Total number of trials)
Empirical probability P(E) = number of trials in which the event happened divided by the total number of trials.
2. A cricketer hit 6 sixes out of 30 balls played. What is the empirical probability that he did NOT hit a six on a ball?
A54
B51
C306
D61
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Answer: A) 54
P(six) = 306=51, so P(not six) = 1−51=54.
3. A die is rolled 120 times. An even number came up 66 times. The empirical probability of an even number is:
A2011
B209
C21
D10066
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Answer: A) 2011
P(even) = 12066=2011=0.55.
4. A company in Bengaluru recorded the monthly salaries of 400 employees. 140 earn below Rs 25000, 180 earn between Rs 25000 and Rs 50000, and the rest earn above Rs 50000. Find the probability that a randomly chosen employee earns above Rs 50000.
5. Two events A and B of an experiment are such that every trial gives exactly one of A or B (they cover all outcomes and never both happen). In 600 trials, A happened 216 times. Find the empirical probability of event B.
A0.64
B0.36
C0.5
D0.46
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Answer: A) 0.64
Since A and B cover all outcomes with no overlap, P(B) = 1 - P(A) = 1−600216=600384=0.64.