The fast food company paid the hamburger bun company $120 per 100 hamburger buns. The fast food company charged their customers the same for 3 hamburger buns as they paid for 5. What was the profit the fast food company made per hundred hamburger buns?

For the fast food company:

Cost of 100 hamburger buns = $120

Hence, cost of 5 hamburger buns = (5*120) / 100 = $6

For the customer:

Cost of 3 hamburger buns = $6

Hence, cost of 100 hamburger buns = (100*6) / 3 = $200

The fast food company bought 100 buns for $120, and sold those 100 buns for $200.

Hence, the profit per 100 buns = 200 - 120 = $80