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Bunuel
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GMAT 1: 640 Q47 V31
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P(pyramid will fall)= 1-P(Pyramid won't fall)
Now, for P(Pyramid won't fall), no card can collapse.
So, P(Pyramid won't fall)= (1-0.05)*(1-0.05)*......12times
=0.95^12
therefore, P(pyramid will fall)= 1-(0.95^12)
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Is it not the same as this question: https://gmatclub.com/forum/a-string-of- ... 31205.html
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Since probability of falling each card is .05, probability of not falling the card willbe 1-0.05 and there are 12 cards which mean probability of not falling any card will be (1-0.05)*12 , so probability that pyramid will collapse in 1 min will be 1-0.95^12

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Hello from the GMAT Club BumpBot!

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