## Online Course Discussion Forum

### Need help on winter camp blue Combinatoris p8, p9 and p10

For #8: The Hint is Spot-on. Remember:

Probability of surviving in spot A_n = n/10 * probability of surviving in spot A_n-1 +

(10-n)/10 * probability of surviving in spot A_n+1

And A_5. Hmmm.... It's not leaned in one way or another.

For #9: Casework with number of heads!

For #10: Geometric sequences can be written as a, ar, ar^2, ar^3, ar^4....ar^29. How can you choose 3 of these such that they are in a geometric sequence. (This is casework with ratio)

Hope these helped! Might have given away too much.

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