Percentages: If no treatment has been given within 3 hours after injury...

falcios

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Can someone please explain how they arrive at the answer? Thanks in advance.


If no treatment has been given within 3 hours after injury to a certain organ, theorgan’s function starts decreasing by 20% each hour. If no treatment has been given with 6 hours after injury, approximately how much function will remain?

Answer
At the end of three hours, the organ still has 100% function.
After 4 hours, it has 80% of that 100%, or (0.8)(1), or 0.8.
After 5 hours, it has 80% of the 80% it had at the end of four hours: (0.8)(.8) equals 64%.
After 6 hours, it has 80% of the 64% it still had after five hours: (0.8)(0.64) equals 0.512.

Can you please explain why 80% is constant after 4 hours not decreasing an additional 20%?

 
If no treatment has been given within 3 hours after injury to a certain organ, theorgan’s function starts decreasing by 20% each hour. If no treatment has been given with 6 hours after injury, approximately how much function will remain?

Answer
At the end of three hours, the organ still has 100% function.
After 4 hours, it has 80% of that 100%, or (0.8)(1), or 0.8.
After 5 hours, it has 80% of the 80% it had at the end of four hours: (0.8)(.8) equals 64%.
After 6 hours, it has 80% of the 64% it still had after five hours: (0.8)(0.64) equals 0.512.

Can you please explain why 80% is constant after 4 hours not decreasing an additional 20%?
I'm sorry, but I don't understand what you're asking...? You are given that the decrease is always ("constantly") 20%. Why would this change, if the percentage is given as being unchanging?
 
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