Answer:
32/225 ≈ 0.1422
Explanation:
If you consider "3-digit" numbers to be between 100 and 999, inclusive, there are 128 such numbers divisible by 7. The probability of choosing one at random is ...
128/900 = 32/225 = 0.1422...(repeating)
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If you consider all non-negative integers less than 1000 to be "3-digit numbers," then the probability is ...
142/1000 = 0.142 (exactly)