A question about a phone number?

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Uno2020-02-25 17:33:29

Probability theory

Uno, 2020-02-25 17:33:29

3 digits have been erased from the phone number. It is necessary to find the probability that among these numbers there are no 1,3 and 5.

343 options in which there are no 1 3 and 5? Doesn't fit.

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SansenSekai, 2020-02-27
@SansenSekai

Problem for 9th grade. 343 options is not a chance.
When tossing a coin, there are 2 meanings: heads and tails. What are the chances of it coming up tails? fifty%. What are the chances of getting tails twice? 25%. What are the chances of getting tails three times? 12.5%.
If the digit in the number is closed, then what is the chance that it will not be 1, 3 or 5? Seven valid values out of 10 possible, and that's 70%. What's the chance that the second digit won't be in that subset either? Third?