1) There is a jar containing 100 marbles: 40 of the marbles are red, 30 are blue, 20 are white, and 10 are black. You are blindfolded and select one marble at random.

a) What is the probability that the marble is black?

b) What is the probability that the marble is black if you are told the marble is not red?

i think that you should ask google for the answer to that problem because if we don't know it google does

geometry: triangles

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call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

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