[hide=B stands for Bernoulli, G stands for Germain]they had two problem sets under those two names[/hide] 

[u]Set 1[/u]


[b]B1 / G1[/b] Find $20^3 + 2^2 + 3^1$.


[b]B2[/b] A piece of string of length $10$ is cut $4$ times into strings of equal length. What is the length of each small piece of string?


[b]B3 / G2[/b] What is the smallest perfect square that is also a perfect cube?


[b]B4[/b] What is the probability a $5$-sided die with sides labeled from $1$ through $5$ rolls an odd number?


[b]B5 / G3[/b] Hanfei spent $14$ dollars on chicken nuggets at McDonalds. $4$ nuggets cost $3$ dollars, $6$ nuggets cost $4$ dollars, and $12$ nuggets cost $9$ dollars. How many chicken nuggets did Hanfei buy?


[u]Set 2[/u]


[b]B6[/b] What is the probability a randomly chosen positive integer less than or equal to $15$ is prime?


[b]B7[/b] Andrew flips a fair coin with sides labeled 0 and 1 and also rolls a fair die with sides labeled $1$ through $6$. What is the probability that the sum is greater than $5$?


[b]B8 / G4[/b] What is the radius of a circle with area $4$?


[b]B9[/b] What is the maximum number of equilateral triangles on a piece of paper that can share the same corner?


[b]B10 / G5[/b] Bob likes to make pizzas. Bab also likes to make pizzas. Bob can make a pizza in $20$ minutes. Bab can make a pizza in $30$ minutes. If Bob and Bab want to make $50$ pizzas in total, how many hours would that take them?


[u]Set 3[/u]


[b]B11 / G6[/b] Find the area of an equilateral rectangle with perimeter $20$.


[b]B12 / G7[/b] What is the minimum possible number of divisors that the sum of two prime numbers greater than $2$ can have?


[b]B13 / G8[/b] Kwu and Kz play rock-paper-scissors-dynamite, a variant of the classic rock-paperscissors in which dynamite beats rock and paper but loses to scissors. The standard  rock-paper-scissors rules apply, where rock beats scissors, paper beats rock, and scissors beats paper. If they throw out the same option, they keep playing until one of them wins. If Kz randomly throws out one of the four options with equal probability, while Kwu only throws out dynamite, what is the probability Kwu wins?


[b]B14 / G9[/b] Aven has $4$ distinct baguettes in a bag. He picks three of the bagged baguettes at random and lays them on a table in random order. How many possible orderings of three baguettes are there on the table?


[b]B15 / G10[/b] Find the largest $7$-digit palindrome that is divisible by $11$.


PS. You should use hide for answers. Rest problems have been posted [url=https://artofproblemsolving.com/community/c3h3132170p28376644]here[/url]. Collected [url=https://artofproblemsolving.com/community/c5h2760506p24143309]here[/url].
1. **B1 / G1** Find \( 20^3 + 2^2 + 3^1 \).

   \[
   20^3 + 2^2 + 3^1 = 8000 + 4 + 3 = 8007
   \]

   \(\boxed{8007}\)

2. **B2** A piece of string of length \( 10 \) is cut \( 4 \) times into strings of equal length. What is the length of each small piece of string?

   Since there are \( 4 \) cuts, there are \( 5 \) pieces.

   \[
   \text{Length of each piece} = \frac{10}{5} = 2
   \]

   \(\boxed{2}\)

3. **B3 / G2** What is the smallest perfect square that is also a perfect cube?

   The smallest perfect square that is also a perfect cube is \( 0 \).

   \(\boxed{0}\)

4. **B4** What is the probability a \( 5 \)-sided die with sides labeled from \( 1 \) through \( 5 \) rolls an odd number?

   Since \( 3 \) of the sides are labeled with odd numbers (they are \( 1, 3, 5 \)), the probability is:

   \[
   \frac{3}{5}
   \]

   \(\boxed{\frac{3}{5}}\)

5. **B5 / G3** Hanfei spent \( 14 \) dollars on chicken nuggets at McDonalds. \( 4 \) nuggets cost \( 3 \) dollars, \( 6 \) nuggets cost \( 4 \) dollars, and \( 12 \) nuggets cost \( 9 \) dollars. How many chicken nuggets did Hanfei buy?

   If Hanfei buys a \( \$9 \) deal, there is no way that he can spend the rest of the money exactly.

   If Hanfei buys \( 0, 1, \) or \( 3 \) \( \$4 \) deals, there is no way that he can spend the rest of the money exactly.

   Therefore, Hanfei needed to have bought exactly \( 2 \) \( \$4 \) deals and exactly \( 2 \) \( \$3 \) deals which means that he bought:

   \[
   2 \cdot 6 + 2 \cdot 4 = 12 + 8 = 20
   \]

   \(\boxed{20}\)

6. **B6** What is the probability a randomly chosen positive integer less than or equal to \( 15 \) is prime?

   First note that there are \( 15 \) positive integers less than or equal to \( 15 \). Since \( 6 \) of them are prime (they are \( 2, 3, 5, 7, 11, 13 \)), the probability is:

   \[
   \frac{6}{15} = \frac{2}{5}
   \]

   \(\boxed{\frac{2}{5}}\)

7. **B7** Andrew flips a fair coin with sides labeled 0 and 1 and also rolls a fair die with sides labeled \( 1 \) through \( 6 \). What is the probability that the sum is greater than \( 5 \)?

   It is obvious that the die must roll at least a \( 5 \). If the die rolls a \( 5 \) (which happens with probability \( \frac{1}{6} \)), the coin must land on \( 1 \), which happens with probability \( \frac{1}{2} \). If the die rolls a \( 6 \) (which happens with probability \( \frac{1}{6} \)), it doesn't matter what the coin lands on.

   Hence, the probability is:

   \[
   \frac{1}{6} \cdot \frac{1}{2} + \frac{1}{6} = \frac{1}{12} + \frac{1}{6} = \frac{1}{12} + \frac{2}{12} = \frac{3}{12} = \frac{1}{4}
   \]

   \(\boxed{\frac{1}{4}}\)

8. **B8 / G4** What is the radius of a circle with area \( 4 \)?

   Let \( r \) be the radius of the circle.

   \[
   \pi r^2 = 4 \implies r^2 = \frac{4}{\pi} \implies r = \sqrt{\frac{4}{\pi}} = \frac{2}{\sqrt{\pi}}
   \]

   \(\boxed{\frac{2}{\sqrt{\pi}}}\)

9. **B9** What is the maximum number of equilateral triangles on a piece of paper that can share the same corner?

   Since the angles of an equilateral triangle are \( 60^\circ \), the maximum number of equilateral triangles on a plane that can share the same corner is:

   \[
   \frac{360^\circ}{60^\circ} = 6
   \]

   \(\boxed{6}\)

10. **B10 / G5** Bob likes to make pizzas. Bab also likes to make pizzas. Bob can make a pizza in \( 20 \) minutes. Bab can make a pizza in \( 30 \) minutes. If Bob and Bab want to make \( 50 \) pizzas in total, how many hours would that take them?

    If Bob and Bab work together, it will take them:

    \[
    \frac{1}{\frac{1}{30} + \frac{1}{20}} = \frac{1}{\frac{5}{60}} = \frac{60}{5} = 12 \text{ minutes to make a pizza.}
    \]

    Hence, it will take them:

    \[
    \frac{12 \text{ minutes}}{1 \text{ pizza}} \cdot 50 \text{ pizzas} = 600 \text{ minutes} = 10 \text{ hours}
    \]

    \(\boxed{10}\)

11. **B11 / G6** Find the area of an equilateral triangle with perimeter \( 20 \).

    Since the perimeter of the equilateral triangle is \( 20 \), the side length is:

    \[
    \frac{20}{3}
    \]

    Hence, by the formula for the area of an equilateral triangle, the area is:

    \[
    \frac{\left(\frac{20}{3}\right)^2 \sqrt{3}}{4} = \frac{\frac{400}{9} \sqrt{3}}{4} = \frac{100 \sqrt{3}}{9}
    \]

    \(\boxed{\frac{100\sqrt{3}}{9}}\)

12. **B12 / G7** What is the minimum possible number of divisors that the sum of two prime numbers greater than \( 2 \) can have?

    First, note that, since the primes are greater than \( 2 \), their sum must be even.

    Hence, their sum must have more than \( 2 \) factors.

    The only case when it can have \( 3 \) factors is if the sum is \( 4 \), which is clearly impossible, so the sum has at least \( 4 \) factors.

    This is achievable when the primes are \( 3 \) and \( 5 \).

    \(\boxed{4}\)

13. **B13 / G8** Kwu and Kz play rock-paper-scissors-dynamite, a variant of the classic rock-paper-scissors in which dynamite beats rock and paper but loses to scissors. The standard rock-paper-scissors rules apply, where rock beats scissors, paper beats rock, and scissors beats paper. If they throw out the same option, they keep playing until one of them wins. If Kz randomly throws out one of the four options with equal probability, while Kwu only throws out dynamite, what is the probability Kwu wins?

    Since there is a \( \frac{1}{2} \) chance that Kwu wins and a \( \frac{1}{4} \) chance that they tie, the probability is:

    \[
    \frac{1}{2} + \frac{1}{4} \cdot \frac{1}{2} + \left(\frac{1}{4}\right)^2 \cdot \frac{1}{2} + \ldots = \frac{1}{2} \left(1 + \frac{1}{4} + \frac{1}{16} + \ldots\right) = \frac{1}{2} \cdot \frac{1}{1 - \frac{1}{4}} = \frac{1}{2} \cdot \frac{1}{\frac{3}{4}} = \frac{1}{2} \cdot \frac{4}{3} = \frac{2}{3}
    \]

    \(\boxed{\frac{2}{3}}\)

14. **B14 / G9** Aven has \( 4 \) distinct baguettes in a bag. He picks three of the bagged baguettes at random and lays them on a table in random order. How many possible orderings of three baguettes are there on the table?

    There are:

    \[
    \binom{4}{3} = 4
    \]

    ways to choose the baguettes and:

    \[
    3! = 6
    \]

    ways to order them, for a total of:

    \[
    4 \cdot 6 = 24
    \]

    \(\boxed{24}\)

15. **B15 / G10** Find the largest \( 7 \)-digit palindrome that is divisible by \( 11 \).

    It is easy to see that the ten largest \( 7 \)-digit palindromes are:

    \[
    9999999, 9988999, 9977999, 9966999, 9955999, 9944999, 9933999, 9922999, 9911999, 9900999
    \]

    Since the first nine are not divisible by \( 11 \) but the tenth is, the answer is:

    \(\boxed{9900999}\)