The rate of ketchup to vinegar should be preserved. Let V be the volume of vinegar that will be used for the larger batch of marinade. Since the recipe uses 7 tablespoons of vinegar for each 3.5 tablespoons of ketchup, then:
[tex]\frac{V}{31.5}=\frac{7}{3.5}[/tex]Then, the volume of vinegar for the larger batch of marinade can be calculated as:
[tex]\begin{gathered} V=\frac{7}{3.5}\times31.5 \\ =63 \end{gathered}[/tex]Therefore, 63 tablespoons of vinegar are needed.
