This is a level 3 number and algebra activity from the Figure It Out theme series.
A PDF of the student activity is included.
Click on the image to enlarge it. Click again to close. Download PDF (426 KB)
use mental strategies to add numbers
Encourage the students to use systematic counting when calculating the cost of the sea creatures. This will involve looking for common shapes and using multiplication rather than shape-by-shape counting. For example, consider this shape:
Question 3 involves students applying the relationship between the number of trapezia in the body of the sea serpent and the total cost of the creature.
A five-trapezia-bodied serpent costs:
Adding five more trapezia will cost another 75c (5 x 15c), which gives a total cost of $2.10.
This can be organised in a table to check (60c + [number of trapezia x 15c]).
Answers to Activity
1. a. 90c
b. 90c
2. $1.35
3. $2.10
4. Answers will vary.