Kara mixes cups of sugar and water in the ratio of 1:2 to make one liter of lemonade. Calculate the total number of cups of sugar used if she used 84 cups to make lemonade.
Step-by-step reasoning:
28
The total ratio for the cups of sugar and water needed to make lemonade is 1 + 2 = 3.

In the 3 cups needed to make one liter of lemonade, the fraction representing the cups of sugar needed is 1 / 3.

If she used 84 cups while making lemonade, she used 1 / 3 * 84 = 28 cups of sugar.

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The final answer: 28