School Style Sloppy Joes

1 pound hamburger
Chopped onion
1/2 cup ketchup with water to make 3/4 cup
1/4 teaspoon dry mustard
1 tablespoon brown sugar
Shake of Worcestershire sauce
1 can tomato soup (undiluted)

Brown hamburger with onion and drain. Add other ingredients and simmer until warm through. Serve over hamburger buns.