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The amount of algae covering the Smith's backyard pond doubled every day until it was completely covered in algae on day 30 of the month. On what day of that month was 75% of the pond algae-free?

 Apr 18, 2019
 #1
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The amount of algae covering the Smith's backyard pond doubled every day until it was completely covered in algae on day 30 of the month. On what day of that month was 75% of the pond algae-free?

 

On day 30 it was 100% covered.

On day 29 it was 50% covered.

On day 28 it was 25% covered, which is the same as 75% algae-free.

 

?

 Apr 18, 2019
edited by Guest  Apr 18, 2019
 #3
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To solve this problem, work backwards.

 

On day 30, it is 100% algae.

On day 29, it is 50% algae.

On day 28, it is 25% algae(or 75% algae free).

 

It was on Day 28.

 

~~Hypotenuisance

 Apr 21, 2019

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