PCAT Quantitative Reasoning – Probability of Random Number Selection
- Apr 19, 2018
- PCAT Question of the Day
When randomly selecting two numbers between 1 and 100, what is the probability that both will be a multiple of 4 or neither will be a multiple of 4? The same number can be chosen twice.
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D is correct. First, let’s identify the probability of selecting two multiples of 4 in a row. The number of multiples of four (4, 8, 12, etc.) is equal to:
Recall that the same number can be selected twice! The probability of both events occurring is equal to the product of their probabilities:
Now let’s determine the probability of neither being a multiple of 4:
The probability of the first situation occurring or the second situation occurring is the sum of their probabilities:
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