Grade 12U Mathematics Problem?

I'm having a bit of trouble figuring out how to solve some math problems. It's Grade 12U Mathematics of >Update:

3) A die is rolled 10 times and 6 times it comes up 5.

(a) What is the probability of this occuring?

(b) Conduct a simulation to show that this is an unfair die.

4) A penny is placed in the bottom row of an eight-by-eight grid. If the penny can be moved one square at a time to the row above, either diagonally or straight ahead, how many paths will lead to the square in the top left-hand corner?

Note: the penny is placed on the 3rd grid from the right (bottom row).

Comments

  • 2 looks more interesting. As such, I will do it.

    P(double 3s on 1 double roll) = 1/36

    P(double 3s are rolled 5 times out of 30) = 30C5*(1/36)^5*(35/36)^25, where 30C5 is the combination operator

    b) P(double 3s never rolled) = (35/36)^30

    P(double 3s rolled at least once) = 1 - (35/36)^30

    1) to get started...

    a) P(3 white marbles in 4) = (10C3)*(6C1)/(16C4)

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