In the recipe, the proportions for the ingredients are as follows: 2 parts borax, 2 parts washing soda, and 1 part flakes.
Let's denote the parts:
- Borax = 2 parts
- Washing soda = 2 parts
- Soap flakes = 1 part
Lenny is using 7 cups of soap flakes, which corresponds to 1 part. Therefore, we can find the total number of parts in the recipe:
- Total parts = 2 (borax) + 2 (washing soda) + 1 (flakes) = 5 parts.
Since 1 part is equal to 7 cups (the amount of flakes Lenny used), we can calculate the amount for the other ingredients:
1 part = 7 cups
Now we can calculate the amounts for borax and washing soda:
- Borax = 2 parts = 2 * 7 cups = 14 cups
- Washing soda = 2 parts = 2 * 7 cups = 14 cups
Now, we need the combined amount of borax and washing soda:
Combined amount = Borax + Washing Soda = 14 cups + 14 cups = 28 cups.
Thus, Lenny needs 28 cups of borax and washing soda combined.