1.

An integer from 300 through 780, inclusive is to be chosen at random. Find the probability that the number is chosen will have 1 as at least one digit.(a) \(\frac{171}{900}\)(b) \(\frac{43}{860}\)(c) \(\frac{231}{546}\)(d) \(\frac{31}{701}\)I got this question at a job interview.I'm obligated to ask this question of Discrete Probability topic in chapter Discrete Probability of Discrete Mathematics

Answer»

The correct answer is (a) \(\frac{171}{900}\)

The best explanation: The number of numbers that don’t have one ANYWHERE 9^3 = 729 is (9 possibilities for each individual digit), and there are 9*10^2 = 900 numbers overall (9 possibilities for hundreds, 10 for the tens and units), so there are 900 – 729 = 171 numbers with at LEAST a one and thus \(\frac{171}{900}\) PROBABILITY.



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