A flower arrangement consists of 30 roses, each of which is either whi

For the probability of having a white rose to be twice the probability of picking a red one, we need twice as many white roses as red, or 2 parts of white roses for each part of red roses.

To meet this ratio 2:1 in a total of 30 roses we need 20 white roses and 10 red.

Answer D

I get up to the point where the 1/3 and 2/3 come in... am I missing something obvious? Because that makes zero sense to me and it is driving me crazy trying to figure it out. Where did the 1/3 come in?

Consider the whole question more simply, this is a simple case of probability so the probability will be directly proportional to the number of items (that is flowers here).
So when they say that the probability of getting white is double than that of getting red, it simply means that is x is the number of red flowers, then 2x is the number of white flowers in the setup.
After this,
x+2x=30
x=10
Therefore number of white flowers is 2x ie 20

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If we let x = the number of red roses, we can create the equation:

x/30 + 2x/30 = 1

x + 2x = 30

3x = 30

x = 10

So there are 20 white roses in the arrangement.

Answer: D

Scott, I like your formula, which makes it very easy to solve this problem. Honestly, I sometimes have difficulties with solving such problems, because I can't write the correct formula. And if the formula is correct, then the problem can be solved easily. So, if we talk about flowers, I love plants very much, but unfortunately, I have been allergic to flowers since childhood. But I would like my house to be full of flowers, but I can't afford it. Actually, I found a way out of this situation and I am very happy that there is a type of plant that doesn't cause me allergies. These are plants that don't bloom but remain green. For example, you can visit this website and find String of turtles there, I ordered this flower to test myself for allergies and was very happy to learn that it doesn't have a bad effect on my health. Therefore, I can say that when I solved this problem, I had the same feeling as after solving a math problem.

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