The number of fish in a lake decreases by x% each year.
given that the number of fish halves in 8 years, work out the value of x.
give your answer correct to 1 decimal place.

The number of fish decreases by x% each year. x% can also be written as 0.01x.

If the total number of fish in a lake is A, after one year the number of fish will be:



After two years the number of fish will be:



So, the general formula for the number of fish after n years can be written as:



It is given that after 8 years, the number of fish is reduced to half. So we can write:



This means the value of x is 8.3%. So, the number of fish in a lake decreases by 8.3% each year

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