Answer:
30%
Explanation:
You want the percentage reduction each year that will result in a reduction of 51% over two years.
Growth factor
The growth factor is 1 added to the growth rate. If the desired growth rate over 2 years is -51%, then the growth factor for that period is ...
1 -51% = 0.49
If the growth factor is the same for each of two years will be ...
(1 +r)² = 0.49 . . . . . . . where r is the growth rate each year
Growth rate
Solving for r gives ...
1 +r = √(0.49) = 0.7
r = 0.7 -1 = -0.3 = -30%
The required growth rate each year is -30%.
The pollution must be reduced by 30% each year for 2 years.
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