Q. There were 18 students running in a race. How many different arrangements of first, second, and third place are possible?Answer:
Calculate Permutations Formula: To determine the number of different arrangements for the first three places, we need to calculate the permutations of 18 students taken 3 at a time. The formula for permutations is P(n,k)=(n−k)!n!, where n is the total number of items and k is the number of items to arrange.
Calculate Factorial of 18: First, we calculate the factorial of 18, which is 18!=18×17×16×…×1.
Calculate Factorial of Difference: Next, we calculate the factorial of the difference between the total number of students and the number of places, which is (18−3)!=15!=15×14×…×1.
Use Permutation Formula: Now, we use the permutation formula P(18,3)=(18−3)!18!=15!18!.
Simplify Expression: We simplify the expression by canceling out the common factorial terms: P(18,3)=118×17×16=18×17×16.
Perform Multiplication: Finally, we perform the multiplication: 18×17×16=4896.