Fair Trades Objective
Students should become experts at making fair trades up and down in any land (base) with or without blocks or counters. When they can do this, they will have demonstrated that they understand how a place value numeration system works — that the base number determines the exchange rate in a land. Then base 10 becomes just another land, and arithmetic becomes meaningful.
Students should also learn that they encounter many different lands in daily living and to account for that in working in those lands. For example, 2 feet 9 inches + 9 inches = 3 feet 6 inches, not 3 feet 8 inches (because feet and inches are in Twelve Land, not Ten Land), and 3 weeks and 1 day less 6 days = 2 weeks and 2 days, not 2 weeks and 5 days (because weeks and days are in Seven Land, not Ten Land).