Fish in the Lake

The 8th graders finished their proportions unit with an activity that extended their work from the R/V Robert G. Brownlee discovery voyage with the Marine Science Institute last year. On the Brownlee, the 8th graders used a drift net to catch and examine different fish in San Francisco Bay. This year they used mathematics to figure out a population in a large body of water by taking a sample.

Their task was to determine the number of “fish” (beans) in their “lake” (a paper bag) as accurately as possible, without actually counting the fish. To do this, the 8th graders used a “net” (a small cup) to take an initial sample. They measured the number of “fish” in their sample and tagged them by replacing the red beans with white ones.

Then, they returned these tagged fish back into their lake. When they took a second sample, they counted how many tagged fish were in their sample, made a ratio, and set it equal to the ratio. Next, students solved for the unknown number of fish in the lake. The 8th graders repeated this process again. If they thought their calculations were close to the actual number of “fish” in the “lake,” they stopped and recorded their work. If they thought another sample would be helpful to get a more accurate total, they repeated the process again. Finally, they counted the total number of beans in the bag and saw how close they were to their calculations. The three groups had varied success-one was within 10% of their total, but all the groups got extra proportion practice in a real-world science application!

#SaklanMath #SaklanHandsOn