Question 1191738
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Any of 10 horses can be first, giving 10 possible options.


Any of remaining 9 horses can be second, giving 9 other possible options.


Any of remaining 8 horses can be third, giving 8 other possible options.


Thus the total number of different possible options is 10*9*8 = 720.    <U>ANSWER</U>
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Solved.


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It is a standard method and a standard mantra for solving such problems.