Lenny is making his own laundry soap. The recipe calls for 2 parts borax, 2 parts washing soda, and 1 part soap flakes. If Lenny uses 7 cups of soap flakes, how many cups of borax and washing soda combined does he need?
The ratio of borax to soap flakes is 2:1, so Lenny needs 2 parts of borax for every 1 part of soap flakes. Since Lenny uses 7 cups of soap flakes, he needs 2/1 * 7 = <<2/1*7=14>>14 cups of borax.
The ratio of washing soda to soap flakes is also 2:1, so Lenny needs 2 parts of washing soda for every 1 part of soap flakes. Since Lenny uses 7 cups of soap flakes, he needs 2/1 * 7 = <<2/1*7=14>>14 cups of washing soda.
Therefore, Lenny needs a total of 14 + 14 = <<14+14=28>>28 cups of borax and washing soda combined. Answer: \boxed{28}.
Since the recipe calls for 2 parts of borax and washing soda combined and 1 part of soap flakes, the total number of parts is 2 + 2 + 1 = 5 parts.
To find out how many cups of borax and washing soda Lenny needs, we can divide the total amount of soap flakes (7 cups) by the total number of parts (5 parts).
Dividing 7 cups by 5 parts gives us 7 cups / 5 parts = 1.4 cups per part.
Since Lenny needs 2 parts of borax and washing soda combined, he will need 1.4 cups per part * 2 parts = 2.8 cups.
To find out how many cups of borax and washing soda Lenny needs, we first need to determine the ratio of soap flakes, borax, and washing soda in the recipe.
The recipe states that Lenny needs 2 parts borax, 2 parts washing soda, and 1 part soap flakes. This means that for every 2 parts of borax and washing soda, there is 1 part of soap flakes.
Since Lenny is using 7 cups of soap flakes, we can determine the total number of parts as follows:
- 2 parts (borax + washing soda) + 1 part (soap flakes) = 3 parts in total
To find the number of parts for borax and washing soda, we need to divide the total parts by the parts per cup of soap flakes:
- Total parts / parts per cup (soap flakes) = Total cups
In this case, since there are 3 parts in total and Lenny is using 7 cups of soap flakes:
- 3 parts / 1 part (for 7 cups of soap flakes) = 3 parts
So, Lenny needs 3 cups of borax and washing soda combined.