Problem: 4 and 1/2 cups of flour plus 1 and 2/3 cups of flour equals
Mrs. F uses 4 1/2 cups of flour to bake rolls. Mrs S uses 1 2/3 times as much
flour to bake rolls. How much flour does Mrs. S use?
You have TWO DIFFERENT problems here.
Saying that Mrs. S uses 1 2/3 times as much flour as Mrs. F is NOT the
same as adding 1 2/3 cups to 4 1/2 cups.
4 1/2 cups + 1 2/3 cups = 4 3/6 cups + 1 4/6 cups = 5 7/6 cups = 6 1/6 cups
4 1/2 cups * 1 2/3 = 9/2 cups * 5/3 = 45/6 cups = 7 3/6 cups = 7 1/2 cups
Which one do you really mean?