How do you figure out the number of combinations in 4 digit numbers?

1 Answer
Jim G.
Apr 13, 2018

#24" combinations"#

Explanation:

#"the possible combinations are"#

#"using the 4 digits 1234"#

#((1,2,3,4),(1,2,4,3),(1,3,2,4),(1,3,2,4),(1,3,4,2),(1,4,2,3),(1,4,3,2))=6((2,1,3,4),(2,1,4,3),(2,3,1,4),(2,3,4,1),(2,4,1,3),(2,4,3,1))=6#

#((3,1,2,4),(3,1,4,2),(3,2,1,4),(3,2,4,1),(3,4,1,2),(3,4,2,1))=6((4,1,2,3),(4,1,3,2),(4,2,1,3),(4,2,3,1),(4,3,1,2),(4,3,2,1))=6#

#rArr" number of combinations "=24#

#"this may be calculated using the "color(blue)"factorial"#

#•color(white)(x)n! =n(n-1)(n-2) ...... xx3xx2xx1#

#"number of combinations "=4! =4xx3xx2xx1=24#

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