Question

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

Answer 1

`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`