Question 1135833: Meteorite falls, also called observed falls, are those meteorites that were witnessed by people or automated devices as they moved through the atmosphere or hit the Earth, and were subsequently collected. All other meteorites are called "finds". The table below shows the (observed) joint distribution of the different types of meteorites, classified by the way the meteorite has been found (find, fall) and by its type (iron, stone). For example, 0.16 is the probability that a stone meteorite is found.
What is the probability that it is iron if it's observed to be falling? Choose the closest answer.
Find Falls
Stones 0.16 0.13
Irons 0.67 0.04
Here's a screenshot of the problem: https://prnt.sc/mrzw06
Answer by jim_thompson5910(35256)   (Show Source):
You can put this solution on YOUR website!
Answer: 0.24 (choice A)
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Explanation on how to get that answer:
The key phrase here is "if it's observed to be falling", meaning that we know 100% it was observed by people or devices. So we can ignore the "finds" column entirely as we know 100% this rock wasn't just found on the ground without observation first.
Add up the values in the "falls" column: 0.13+0.04 = 0.17, so this tells us that 17% of the rocks were observed
Of this 17%, we see that 4% are iron since 0.04 is the decimal equivalent to 4%
Divide 0.04 over 0.17 to get
0.04/0.17 = 0.23529411764706
and then round to 2 decimal places
0.23529411764706 becomes 0.24 (representing roughly a 24% chance)
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