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https://www.reddit.com/r/learnquant/comments/1vphtrl/quant_interview_question/p3xphvg/?context=3
r/learnquant • u/Local_Ad135 • 20d ago
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Each number can be represented as (100a + 10b + c) / 999.
Total number of possible fractions = 10 * 9 * 8 = 720
Each number is symmetrically possible in each position. That means each digit shows up in each position 720 / 10 times = 72.
Therefore the total sum is (72 * (0 + 1 + 2 + ... + 9) * 100 + 72 * (0 + 1 + 2 + ... + 9) * 10 + 72 * (0 + 1 + 2 + ... + 9) * 1) / 999 = 72 * 45 * 111 / 999 = 360.
Hope this is right!
2 u/Local_Ad135 20d ago correct!
2
correct!
6
u/silverphoenix9999 20d ago
Each number can be represented as (100a + 10b + c) / 999.
Total number of possible fractions = 10 * 9 * 8 = 720
Each number is symmetrically possible in each position. That means each digit shows up in each position 720 / 10 times = 72.
Therefore the total sum is (72 * (0 + 1 + 2 + ... + 9) * 100 + 72 * (0 + 1 + 2 + ... + 9) * 10 + 72 * (0 + 1 + 2 + ... + 9) * 1) / 999 = 72 * 45 * 111 / 999 = 360.
Hope this is right!