Hello, epetrik!
1. A gambler sets up a game in which she puts four $10 bills and one $20 bill in one box.
A player randomly tales one of the bills and keep it.
To break even on average, how much must the gambler charge the player to play?
The player will draw: . ![\begin{array}{c}\text{a \$10-bill }\frac{4}{5}\text{ of the time} \\ \\[-4mm]<br />
\text{a \$20-bill }\frac{1}{5}\text{ of the time} \end{array}](http://latex.codecogs.com/png.latex?\begin{array}{c}\text{a \$10-bill }\frac{4}{5}\text{ of the time} \\ \\[-4mm]<br />
\text{a \$20-bill }\frac{1}{5}\text{ of the time} \end{array})
In five games, the gambler can expect to pay out $10, $10, $10, $10, $20
. . a total of $60 over 5 game.
That is, he can expect to pay out an average of
per game.
To break even, the gambler should charge $12 per game.
2. Brittany pays $4.00 for a square piece of wood,
which she makes into a stop sign by cutting the corners off.
What is the cost of the wasted parts? A stop sign is tranditionally a regular octagon. Code:
: - - - x - - - :
- * - - * * * * - - *
: | * * |
: | * * |
: * *
: * *
x * *
: * *
: * *
: | * x-2a * | a
: | * * |
- * - - * * * * - - *
: a : x-2a: a :
The square board is
feet.
. . She paid $4 for
square feet of wood.
Let the corner pieces be 
Then the side of the octagon is 
At the lower-right, we have an isosceles right triangle
. . with equal sides
and hypotenuse
.
Pythagorus: . ^2 \:=\:a^2 + a^2 \quad\Rightarrow\quad 2x^2 - 4xa + x^2 \:=\:0)
Quadratic Formula: . x )
Since
, we have: . 
The area of the four triangles is: .
square feet
The fraction of wasted wood is: . x^2}{x^2} \:=\:3-2\sqrt{2} )
The cost of the wasted wood is: . (\$4) \;\approx\;\$0.68)