I. The final problem set from the "Measuring Polygons" unit of the 5th grade TERC/Investigations Student Activity Workbook (Unit 5, p. 63) [click to enlarge]:
II. The final exercise from the "Perimeter, Area and Surface Area" unit of the 5th grade Singapore Math Primary Mathematics 5A Workbook (Unit 5, p. 122) [click to enlarge]:
III. Extra Credit:
What do you think is meant by "size" in the Investigations problem above? Does doubling the sides of a swimming pool actually double its "size"?