4.(6/100)×X=25440
X=(25440×100):6=424000
3.
[tex]C_{n}^{k} = \frac{n!}{k!(n-k)!} \\ C_{4}^{1}= \frac{4!}{1!(4-1)!} = \frac{1*2*3*4}{1*2*3} =4 \\ C_{4}^{0}=1 \\ C_{4}^{2}= \frac{4!}{2!(4-2)!} = \frac{1*2*3*4}{1*2*1*2} =6 \\ \\ C_{4}^{3}= \frac{4!}{3!(4-3)!} = \frac{1*2*3*4}{3*1} =8 \\ \\ 1+4+6+8=23[/tex]
1. Permutari de 6=1×2×3×4×5×6=720
2. Aranjamente de 7 luate cate 4
[tex]A_{n}^{k} = \frac{n!}{(n-k)!}=A_{7}^{4} = \frac{7!}{(7-4)!}= \frac{1*2*3*4*5*6*7}{1*(2*3}=4*5*6*7= 840[/tex]
