Amanda is making pastry dough. she mixes of a 1/3cup of flour and of a 1/5 cup of sugar. if she wants to mix flour and sugar in the same ratio to make 16 cups of pastry dough, how many cups of flour and sugar will she need?

Flour : sugar = (1/3) : (1/5) = 5 : 3 . . . . . . . . multiply the first ratio by 15 to eliminate fractions

The total of ratio units in the last representation is 5+3=8, so for a recipe of 16 cups, each ratio unit will stand for 16/8 = 2 cups.

Multiplying the ratio by 2 cups, we find Amanda will need

... 10 cups flour : 6 cups sugar

for her recipe.

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