Abag has 4 green marbles, 3 red marbles, and 3 yellow marbles. what is the probability that you pick a yellow marble, do not replace it, and pick a red marble?

1/10

Explanation: 3/9 times 3/10 equals 9/90, simplify and you'll get 1/10

There are 3 red, that is where the first numerator comes from and there are 10 marbles so that is where the denominator comes from. There are 3 yellows, hence the second numerator but as we have taken a marble out there are now only 9 marbles in total.

take it another

geometry: triangles

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answers archive

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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