Is a sub section in Schoenfeld’s Mathematical Problem Solving. The argument is that when two students work together, this interaction can spur cognitive development resulting in approaches to the problem being solved that are qualitatively different than those taken by the students on their own.
But if Vygotsky is not one’s cup of tea, how about this problem also from the book.
Ten people are seated around a table. The average income of these 10 people is $10000. Each person’s income is the average of the people sitting immediately to his left and right. What is the possible range of incomes for each person?