C

1003020901

Level: 
C
Let there be vectors: \(\vec{a}=(1,3,-1)\), \(\vec{b}=(0,3,1)\), \(\vec{c}=(-1,2,2)\). Find \(\vec{a}\times\vec{b}\) and \(\left(\vec{a}\times\vec{b}\right)\cdot\vec{c}\).
\(\vec{a}\times\vec{b}=(6,-1,3), \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=-2\)
\(\vec{a}\times\vec{b}=8, \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=(-8,16,16)\)
\(\vec{a}\times\vec{b}=(-6,1,-3), \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=2\)
\(\vec{a}\times\vec{b}=\sqrt{46}, \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=2\)

9000153906

Level: 
C
Find the number of ways how to distribute \(5\) identical balls among \(8\) persons so that no persons gets more than one ball.
\(\frac{8!} {5!3!} = 56\)
\(\frac{8!} {3!} = 6\:720\)
\(\left({12\above 0.0pt 8} \right) = 495\)
\(\left({12\above 0.0pt 5} \right) = 792\)