A recipe calls for 2 cup so of flour, 1/4 cup sugar, 1/3 cup milk. What Ismaili the total volume of the three ingredients?

Easiest would be just crosscheck 1 by 1,

like, first check for flour, he has 15 cups, i. e. 15/2.5 = 6 cups can be made.

then come to sugar, sugar per cup (if he wants to make 6 cups of recipe) = 16/6 = 2+2/3 (what he has), but he need 2+3/4; so not available.

So, ans = 5