Thursday, April 15, 2010
Bulb Or No Bulb?
There are 100 bulbs arranged in a row. Each bulb has its own switch and is currently turned off. In the first round, you turn every switch on. In the second round, you flip the switch of every second bulb (i.e. bulb 2, 4, 6, 8 and so on). In the third round, you flip the switch of every third bulb and so on. What is the state of bulb 9 after 100 rounds? Also, how many bulbs are on after 100 rounds?
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after 100 rounds 9th bulb is ON..
ReplyDeletetotal 10 bulbs are ON after 100 rounds...(i.e perfect squares 1 4 9 16 25 36...)