word problem

Question

Biologists tagged 500 fish in a lake.  At a later date they found 7 tagged fish in a sample of 700 fish.  Estimate the total number of fish in the lake to the nearest hundred

Answer 1

Liz,

Assuming that sample was fairly representative of the entire lake, 7 tagged fish in a sample of 700 means that on average 7/700 or 1/100, or for every tagged fish, there are 100 fish in the lake.

 

Then 100 * 500 fish that the Biologists tagged = 50,000 total fish population in lake (approximate)

of which 500 are tagged and 49,500 are untagged.