Which statement is true about permutations versus combinations?

Study for the NBCT Mathematics AYA Component 1 exam. Utilize flashcards and multiple-choice questions with detailed explanations for each question. Prepare efficiently for success in your teaching certification journey!

Multiple Choice

Which statement is true about permutations versus combinations?

Explanation:
The essential idea is how order affects counting. In permutations, the sequence matters: picking items in a certain order produces distinct results. For example, from three items A, B, C, choosing two gives six different ordered arrangements: AB, AC, BA, BC, CA, CB. In contrast, combinations ignore the order of the chosen items. From the same set, choosing two items yields three distinct groups: {A,B}, {A,C}, {B,C}. The same two items in a different order aren’t counted separately. That difference shows why the statements are true or false. The fact that the count for permutations uses nP r = n!/(n−r)! while combinations use nC r = n!/(r!(n−r)!) reflects the order distinction: the r! in the denominator for combinations removes the order factor. So it’s correct to say permutations count order, while combinations do not.

The essential idea is how order affects counting. In permutations, the sequence matters: picking items in a certain order produces distinct results. For example, from three items A, B, C, choosing two gives six different ordered arrangements: AB, AC, BA, BC, CA, CB. In contrast, combinations ignore the order of the chosen items. From the same set, choosing two items yields three distinct groups: {A,B}, {A,C}, {B,C}. The same two items in a different order aren’t counted separately.

That difference shows why the statements are true or false. The fact that the count for permutations uses nP r = n!/(n−r)! while combinations use nC r = n!/(r!(n−r)!) reflects the order distinction: the r! in the denominator for combinations removes the order factor. So it’s correct to say permutations count order, while combinations do not.

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