Raymond B. answered • 05/04/21
Tutor
5
(2)
Math, microeconomics or criminal justice
1) 10x9x8x7x6x5x4x3x2x1 = 10!/(10-10)! = 10!/1! = 10!
=3628800
2) 10x9x8x7x6x5x4 = 10!/(10-7)! = 10!/3!
= 604800
how many with 1 digit & none repeated? 10!/(10-1)! = 10!/9! = 10 ways
0,1,2, ...8,9
how many with 2 digits & none repeated? 10 x9= 10!/(10-2)! =10!/8! = 90 ways
01
02
03
...
09 9 ways
10
12
13
...
19 9 ways
20
21
23
24
...
29 9 ways
...
90
91
92
...
98 9 ways
10x9 = 90 ways
