proportion work problems

Question

Set up and solve a proportion. Use a calculator if it is helpful.

A perfume is to be mixed in the ratio of 3 drops of pure essence to 7 drops of alcohol. How many drops of pure essence should be mixed with 42 drops of alcohol?

      drops

Answer 1

A ratio means a fraction like 3/4, also written as 3:4.

 

Here we have two ratios; and they are equal!

 

                the mix               =         desired

     (3 essence) / (7 alcohol) = (x essence) / (42 alcohol)

     3/7 = x/42

     7x = 3(42)             [cross-multiply]

       x = 3(42)/7          [divide both sides by 7]

       x = 3(6)

       x = 18 drops of pure essence