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Probability - Quant/Math - CAT 2010
Question 4 the day:
October 10, 2003
The question for the day is from the topic of Probability.
- A number is selected at random from first thirty natural numbers. What is the chance that it is a multiple of either 3 or 13?
| (1) |
17/30 |
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(2) |
2/5 |
| (3) |
11/30 |
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(4) |
4/15 |
Correct Answer - (2)
Solution:
The probability that the number is a multiple of 3 is 10/30. (Since 3*10 = 30).
Similarly the probability that the number is a multiple of 13 is 2/30. {Since 13*2 = 26).
Neither 3 nor 13 has common multiple from 1 to 30. Hence these events are mutually exclusive events. Therefore chance that the selected number is a multiple of 3 or 13 is (10+2)/30 = 2/5
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