A mother is making her own bubble mix out of dish soap and water for her two-year-old son.  The recipe she is following calls for 3 tablespoons of soap for every 1 cup of water.  If the container she hopes to store the bubble mix in can hold 40 ounces of liquid, and there are 8 ounces in a cup of water, how many tablespoons of soap should she add to the container (assuming that the soap itself doesn't count towards the capacity of the container)?
The 40-ounce container can hold 40/8 = <<40/8=5>>5 cups of water.
This means that 5*3 = <<5*3=15>>15 tablespoons of soap should be used, since each cup of water requires 3 tablespoons of soap.
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