# Posts by Zeneth

Total # Posts: 3

**Math**

Five red cards numbered 1,2,3,4,5 and two black cards both numbered 5 are randomly ordered face-down into a pile. The cards are flipped over one at a time until either the sum of the numbers on the red cards is at least 10, or the sum of the numbers on the black cards is at ...

**Math**

Find the smallest prime number N such that the following is true: The largest prime factor of N−1 is A; The largest prime factor of A−1 is B; The largest prime factor of B−1 is 7.

**Math**

9 fair coins are independently tossed in a row. Let X be the random variable denoting the number of instances in which a Head is immediately followed by a Tail during these 9 tosses. The variance of X has the form a/b, where a and b are coprime integers. What is the value of a...