This problem solving activity has a number focus.
Some octopuses, fish and a few mermaids are in a rock pool.
Altogether there are 38 arms, 24 eyes and 8 tails in the pool.
How many mermaids are there?
Students are likely to use logical deduction, guess and check, or make a table to solve this problem.
It is similar to the Level 2 Number problem, Pigs and Ducks.
Some octopuses, fish and a few mermaids are in a rock pool. Altogether there are 38 arms, 24 eyes and 8 tails in the pool.
How many mermaids are there?
Write a problem like this one that has three different types of creatures and three body parts.
This is helpful information that can be deduced: Fish don’t have arms so the arms come from the octopuses and the mermaids. All of the creatures have two eyes and since there are 24 eyes there must be 12 creatures. Octopuses don’t have tails so there are 8 fish and mermaids.
Therefore, there are 12 creatures, 8 of which are fish and mermaids, and 12 – 8 = 4 octopuses.
4 octopuses contribute 4 x 8 = 32 arms. That leaves 38 – 32 = 6 arms for the mermaids. There must be 3 mermaids.
The problem can also solved using a diagram, a table, or by using guess and check. If a group uses guess and check and gets the right answer, you might like to suggest that they try to find another way.
Printed from https://meaningfulmaths.nt.edu.au/mmws/nz/resource/rock-pool at 8:56pm on the 26th February 2024