A owes $100 to B. B owes $80 to C. C owes $80 to D. D owes $90 to E. Total debt is $350. A pays $100 to B. B keeps $20 and pays $80 to C. C pays $80 to D. D ad

A owes $100 to B. B owes $80 to C. C owes $80 to D. D owes $90 to E. Total debt is $350. A pays $100 to B. B keeps $20 and pays $80 to C. C pays $80 to D. D adds $10 of his own money to pay $90 to E. Everyone's debt has been repaid, but only $110 of currency is needed for all these transactions to take place -- assuming all debts are paid in cash. All you need is sufficient liquidity. I could loan you five quadrillion dollars provided that you also loan me five quadrillion dollars. No currency has changed hands, but we've just increased the world's total outstanding debt by ten quadrillion dollars!