Answer:
The number of ways to choose a set of 9 pencils from a selection of 10 is 10.
Step-by-step explanation:
According to the combination formula, the total number of ways to select r items from total n items is
[tex]^nC_r=\frac{n!}{r!(n-r)!}[/tex]
Total number of pencils = n = 10
Number of selected pencils = r = 9
The number of ways to choose a set of 9 pencils from a selection of 10 is
[tex]^{10}C_{9}=\frac{10!}{9!(10-9)!}[/tex]
[tex]^{10}C_{9}=\frac{10\times 9!}{9!1!}[/tex]
[tex]^{10}C_{9}=10[/tex]
Therefore the number of ways to choose a set of 9 pencils from a selection of 10 is 10.