Exercise · ZW-SYMMETRIC-GROUP-008 · ★★☆ Intermediate
For which \(n\) does \(S_n\) have exactly \(120\) elements?
Choose one option.
Show answer
- D. \(n=5\)
Explanation
Since \(|S_n|=n!\) and \(5!=120\), we need \(n=5\). With \(n=4\) there are \(24\) and with \(n=6\) there are \(720\).
Review the concept: Symmetric group
The symmetric group \(S_n\) is the set of bijections \(\sigma\) of \(\{1,\dots,n\}\) onto itself, with composition \(\sigma\tau\) as the operation.
\[(\sigma\tau)(i)=\sigma(\tau(i))\]
More practice problems: symmetric group
- ZW-SYMMETRIC-GROUP-001 How many elements does S_4 have?
- ZW-SYMMETRIC-GROUP-002 Write a permutation of S_3 as the list [σ(1),σ(2),σ(3)]. If σ=[2,3,1] and τ=[2,1,3], what is στ (τ…
- ZW-SYMMETRIC-GROUP-003 What is the identity element of S_5?
- ZW-SYMMETRIC-GROUP-004 If σ=[2,3,1,4] in S_4 (list [σ(1),…,σ(4)]), what is σ^-1?
- ZW-SYMMETRIC-GROUP-005 What is the smallest n for which S_n is not abelian?
- ZW-SYMMETRIC-GROUP-006 How many permutations σ∈ S_5 satisfy σ(1)=1?
- ZW-SYMMETRIC-GROUP-007 Which statement about S_n is true?
- ZW-SYMMETRIC-GROUP-009 In S_4 let σ=[2,1,3,4] and τ=[1,3,2,4]. What is (στ)(2)?