MHB Probability of Student Seating Arrangement in Height Order

rainbow1
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a class has 9 students who are to be assigned seating by lot. What is the probability that students will be arranged in order from shortest to tallest? (assume that no two stusents are the same height.)
 
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Same as picking 9 balls numbered 1 to 9 at random:
probability that order will be 1,2,3,4,5,6,7,8,9 ?
 
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