Final answer:
Kevin should use 14 fluid ounces of concentrated soap with 84 fluid ounces of water to make his all-purpose cleaner according to the given ratio of 4 fluid ounces of soap to every 3 cups of water.
Step-by-step explanation:
To determine how much concentrated soap Kevin should use with 84 fluid ounces of water, we have to use the ratio provided in the directions. The ratio states 4 fluid ounces of soap for every 3 cups of water. First, we must convert the water from ounces to cups, knowing that 8 fluid ounces equals 1 cup.
84 fl oz ÷ 8 fl oz/cup = 10.5 cups of water.
Now, we set up a proportion with the soap to water ratio:
4 fl oz soap / 3 cups water = x fl oz soap / 10.5 cups water
To solve for x (amount of soap), we cross multiply and divide as follows:
3 * x = 4 * 10.5
3x = 42
x = 42 ÷ 3
x = 14
Therefore, Kevin should use 14 fluid ounces of soap with 84 fluid ounces of water to make the all-purpose cleaner as per the given ratio.