Open ended math problem

When studying multiples of numbers, students can learn to use multiples to make combinations using open ended problems.

On the web, have students practice on: http://www.vtaide.com/png/legs.htm. The Parade of Legs is an open ended problem where students use multiplication and division to solve it. The applet allows them to try different math strategies in a low stress setting.

When students are familiar with the process, give the students the following problem:
Julio was at the aquarium when he saw a number of crabs and octopus crawling or swimming by. He counted all the legs of the crabs and octopi and found that the total number of legs add up to 108. How many of each kind of animals (crabs and octopi) passed by? How many combinations can you find?

In pairs, have them work out a table to show possible combinations. They can use calculators if needed to check answers. Have them create a finished product using Microsoft Word. Use a teacher created rubric to evaluate. There are four possible combinations: 96 legs -12 octopi and 12 legs-2 crabs, 72 legs – 9 octopi and 36 legs- 6 crabs, 48 legs – 6 octopi and 60 legs- 10 crabs, 24 legs- 3 octopi and 84 legs – 14 crabs. The rubric should also include grading on information that is clear and organized and correct usage of all tools (calculators, computers).