Joaquin will need 2 and four fifths cups.
Proportion is an equality between ratios. Two ratios are proportional when the result of dividing the numerator and denominator of the first ratio is equal to the result of dividing the second.
With that said, if Joaquin wants to follows the original recipe he will need to increase the quantite of butter, but proportionately. Thus:
1/2 of a cup of butter -- serves 5 people
x cup of butter -- serves 28 people
5x = 14
x = 14/5 = 2,8
Therefore, Joaquin will need 2 and four fifths cups.
See more about math at: brainly.com/question/17387142
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