5/4 • 200/1, 1000/4
which is 250
250 is 1 1/4 of 200
If you cut the rectangle (the wall) diagonally, you get two congruent triangles. The measurements of the sides of one the triangles is 8, 15 and x. There is a pythagorean triples 8, 15, 17 so x has to be 17. if you dont know the triple you can do a^2 + b^2 = c^2 8^2 + 15^2 = c^2 c = 17
the diagonal of wall should be 17
Total number of sheets are 12.
Total number of white sheets= 9
Total number of red sheets = 3
Probability = Number of favorable outcomes/ total number of outcomes.
Hence
When Calvin throws the sheets in the air, the probability that he gets a white sheet is

which equals to 
that becomes 0.75