Question

jenny makes plaster using a ratio of 4 cups of water to 5 pounds of plaster powder. whose plaster recipe uses more water? use the ratio table here and in exercise 4 to compare. kevin and jenny each use 12 cups of water to make plaster. who will make more plaster? explain.

Explanation:

Step1: Find the ratio for Kevin's recipe

The first - table shows a ratio. Let's assume the ratio of cups of water to pounds of powder for Kevin is constant. If 3 cups of water are used with 4 pounds of powder, the ratio is $\frac{3}{4}= 0.75$ cups of water per pound of powder.

Step2: Find the ratio for Jenny's recipe

Jenny's ratio is 4 cups of water to 5 pounds of powder. The ratio is $\frac{4}{5}=0.8$ cups of water per pound of powder. Since $0.8>0.75$, Jenny's recipe uses more water per pound of powder.

Step3: For the second - part, find the amount of powder for Kevin when using 12 cups of water

Let the amount of powder be $x$ pounds. Using the ratio $\frac{3}{4}=\frac{12}{x}$. Cross - multiply: $3x = 4\times12$, so $3x=48$, and $x = 16$ pounds.

Step4: For the second - part, find the amount of powder for Jenny when using 12 cups of water

Let the amount of powder be $y$ pounds. Using the ratio $\frac{4}{5}=\frac{12}{y}$. Cross - multiply: $4y=5\times12$, so $4y = 60$, and $y = 15$ pounds.
Since $16>15$, Kevin will make more plaster when using 12 cups of water.

Answer:

Jenny's recipe uses more water. Kevin will make more plaster when using 12 cups of water.