Question

Justin is mixing punch for his birthday party. His recipe calls for 2 1/2 cups of cranberry juice and serves 12 people. Using the recipe, how many more cups of cranberry juice are needed to make punch for 18 people than are needed to make punch for 12 people?

Answer 1

1,15 cups more, as 18 people need 3,75 cups

Answer 2

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12 people:
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$\text { 12 people = } 2\dfrac{1}{2} \text { cups}$

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Find 1 person:
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$\text { 1 person = } 2\dfrac{1}{2} \div 12 \text { cups}$

$\text { 1 person = } \dfrac{5}{2} \times \dfrac{1}{12} \text { cups}$

$\text { 1 person = } \dfrac{5}{24} \text { cups}$

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Find 18 person:
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$\text { 18 person = } \dfrac{5}{24} \times 18 \text { cups}$

$\text { 18 person = } \dfrac{15}{4} \text { cups}$

$\text { 18 person = } 3\dfrac{3}{4} \text { cups}$

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Find the difference:
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$3\dfrac{3}{4} - 2\dfrac{1}{2} \text$

$= 3\dfrac{3}{4} - 2\dfrac{2}{4} \text$

$= 1\dfrac{1}{4} \text { cup}$