The Quant 7514 / 75
MediumBrain Teasers
100 Lockers
GoogleTwo Sigma
100 lockers start closed. Person i (for i = 1…100) toggles every locker that is a multiple of i. After all 100 people pass, how many lockers are open?
Approach
How many times is locker n toggled?
Which numbers have an odd number of divisors?
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