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# Fish Tank

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Finn’s fish store has 5 tanks of goldfish; each tank holds 40 fish. He collects and inspects 5 fish from each tank and finds that 4 fish have fin rot. Find the estimated number of goldfish in the store that have fin rot.

May 19, 2021

The sample has 25 fish, 5 from each tank. The ration of fish rot in the sample is $$\frac{4}{25}.$$ The store has a total of 5(40) = 200 fish, the population the sample of 25 comes from. The assumption is that if the sampling is done randomly the ratio of fish rot in the population would be the same as that of the sample. So we can expect$$\frac{4}{25}(200)=32$$ fish with fish rot in the whole store.