Answer: 455
Step-by-step explanation:
Given: There are 15 exercise bikes in a fitness store showroom.
To select 3 of them we will use " combinations".
The number of combinations of selecting r things out of n is given by :-
[tex]^nC_r=\dfrac{n!}{r!(n-r)!}[/tex]
So, the number of combinations of selecting 3 bikes out of 15 = [tex]^{15}C_3[/tex]
[tex]=\dfrac{15!}{3!(15-3)!}\\\\=\dfrac{15\times14\times13\times12!}{3\times2\times12!}\\\\=5\times7\times13\\\\=455[/tex]
Hence, the number of ways a group of three be selected = 455
