## anonymous one year ago Maggie has 7 tiles with pictures of plants and 2 tiles with pictures of animals. Maggie keeps all the tiles on a mat with the pictures hidden and mixes them up. She then turns one tile face up and finds the picture of a plant on it. She removes this tile from the mat and turns over another tile without looking. What is the probability that the second tile that Maggie turns over has a plant on it?

1. anonymous

@Turn_and_Burn

2. marco26

Let me try it. First, let's draw a probability tree:|dw:1443247540178:dw| where P represents the probability of plants and A the probability of animals. There are total of 9 tiles so for the first pick the probability of picking a plant is 7/9 and 2/9 for picking an animal. Suppose the first pick is a plant and this tile has been removed from the mixture (as stated in the problem) , the probability of picking a plant and an animal for the second time is now equal to 6/8 and 2/8, respectively.

3. marco26

We're interested in the encircled part of the probability tree since it is stated that the first pick is a plant. |dw:1443248009893:dw|, then for the second time:$P(plant)=\frac{ (\frac{ 7 }{ 9 })(\frac{ 6 }{ 8 }) }{ (\frac{ 7 }{ 9 })(\frac{ 6 }{ 8 })+\frac{7 }{ 9} (\frac{2}{8})}=3/4$ I'm not 100 % sure about this though. others can correct if I'm wrong but I think this is correct. :)