Q. Luis is packing a bag for vacation. He has 9 unique shirts, but he can only fit 5 in his bag.How many different groups of 5 shirts can he take?◻
Identify Problem: Luis has 9 unique shirts and wants to choose 5 for his bag. This is a combination problem, not permutation, since the order doesn't matter.
Use Combination Formula: To calculate combinations, we use the formula: C(n,k)=k!(n−k)!n!
Substitute Values: Plug in the values: C(9,5)=5!(9−5)!9!
Simplify Denominator: Simplify the denominator: C(9,5)=(5!4!)9!
Calculate Factorials: Calculate the factorials: 9!=9×8×7×6×5!, 5!=5×4×3×2×1, and 4!=4×3×2×1
Cancel Common Factorial: Cancel out the common 5! in numerator and denominator: C(9,5)=4×3×2×19×8×7×6
Perform Calculation: Perform the calculation: C(9,5)=4×3×2×19×8×7×6=19×2×7×6=126