Mona asked in Science & MathematicsBiology · 10 years ago

# Population problem - biology?

In a study, 5000 flies were captured and marked with a powder and released.

The next day, 515 flies were captured and 21 of them had marks

how many flies are in the population?

I don't know how to do it. Does it have to do with percentage?

Relevance
• 10 years ago

N=MC/R

where

N = Estimate of total population size

M = Total number of animals captured and marked on the first visit

C = Total number of animals captured on the second visit

R = Number of animals captured on the first visit that were then recaptured on the second visit

M=5000

C=515

R=21

Easy math gives you

N=(5000*515)/21

N=122,619 flies in that population

• 10 years ago

Yes. Set up equivalent proportions for the size of the population / number marked:

515 in captured population / 21 marked = x in total population / 5000 marked. Then just solve for x → (5000/21) x 515 = x =122,619.

Source(s): Forty years teaching Biology, currently teaching College Math Refresher course