Lesson 8-2: Estimating Population Size

You catch, tag, and release 50 fish back into a pond. Then, you catch 25 more fish, 5 of which are tagged. What is the best estimate of the number of fish in the pond?

• 100 fish

• 250 fish

• 400 fish

• 625 fish

Miki, a graduate student, needed to estimate how many catfish were in a local river. First, she marked 590 catfish with tags. Later, she captured 700 catfish, of which 59 had tags. To the nearest whole number, what is the best estimate for the catfish population?

• 6000 catfish

• 6500 catfish

• 7000 catfish

• 5500 catfish

During a study on the local armadillo population, a wildlife researcher put tags on 80 armadillos. Several weeks later, the researcher caught 150 armadillos and saw that 15 of them had tags. To the nearest whole number, what is the best estimate for the armadillo population?

• 800 armadillos
• 400 armadillos
• 500 armadillos
• 450 armadillos

A worker at a local aquarium is instructed to estimate the population of sardines in the tank. She catches 170 sardines, marks them with special paint, and returns them to the tank. Then she catches 330 sardines and finds that 17 of them are marked. To the nearest whole number, what is the best estimate for the sardine population?

• 3200 sardines

• 3300 sardines

• 3500 sardines

• 3600 sardines

Some researchers wanted to monitor the trout population, so they marked 830 trout with tags. Later, they captured 720 trout and found that 72 of them had tags. To the nearest whole number, what is the best estimate for the trout population?

• 8300 trout
• 8100 trout
• 7900 trout
• 8200 trout

A researcher who was conducting a study caught, tagged, and released 35 opossums. Weeks later, the researcher caught a total of 360 opossums, of which 14 were tagged. To the nearest whole number, what is the best estimate for the opossum population?

• 800 opossum

• 900 opossum

• 850 opossum

• 875 opossum

In order to estimate the number of scorpions living in a region in California, Stanley traps 24 scorpions and marks them with special paint. He releases the scorpions and then later traps 370. Of these, 12 are marked. To the nearest whole number, what is the best estimate for the scorpion population?

• 740 scorpions
• 750 scorpions
• 725 scorpions
• 800 scorpions

A country in Africa is trying to restore its zebra population and is carefully keeping track of how many zebras are in the area. To do so, local wildlife authorities put tags on 56 zebras and release them. Later, they corral 460 zebras; among those zebras, 28 were tagged. To the nearest whole number, what is the best estimate for the zebra population?

• 920 zebras
• 915 zebras
• 925 zebras
• 930 zebras

Scientists researching amphibians put tags on 26 frogs in a wetland area. Later, the scientists captured 250 frogs, of which 10 had tags. To the nearest whole number, what is the best estimate for the frog population?

• 675 frogs

• 625 frogs

• 775 frogs

• 650 frogs

Scientists captured, tagged, and released 95 ducks as part of a research study. A week later, the scientists returned to the area and found 20 tagged ducks out of the 160 ducks they counted. To the nearest whole number, what is the best estimate for the duck population?

• 700 ducks

• 750 ducks

• 650 ducks

• 760 ducks