Answer:
[tex]\dfrac{1}{30}[/tex]
Step-by-step explanation:
6 symbols and 4-symbol code so number of combinations wich doesn't contain the same symbol twice would be:
6•5•4•3 = 360
If code starts with a star followed by triangle that means only one posibility for first two symbols and code doesn't containing the same symbol twice means that left 4 symbols for next two.
So number of combinations of code starting with a star followed by triangle and doesn't containing the same symbol twice will be:
1•1•4•3 = 12
The probability that a randomly chosen code starts with a star followed by triangle and doesn't contain the same symbol twice:
[tex]\dfrac{1\cdot1\cdot4\cdot3}{6\cdot5\cdot4\cdot3}=\dfrac{1\cdot1}{6\cdot5}=\dfrac{1}{30}[/tex]
