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ISI2015PCBA3
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Consider all possible permutations of eight distinct elements $a, b, c, d, e, f, g, h$. In how many of them, will $d$ appear before $b$? Note that $d$ and $b$ may not necessarily be consecutive.
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isi2015pcba
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May 29, 2016
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jothee
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8!/2! as (d,b) is the only permitted arrangement between d and b , so it is equivalent to treating them as similar objects.
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May 29, 2016
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Prasita Mukherjee
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d,b is not the only arrangement. d,a,c,b is also permitted. consecutive not necessary
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d should be placed before b.
answer in pic (courtesy: friend)
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May 8, 2018
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Debasmita Bhoumik
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