Lenny is making his own laundry soap. The recipie 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?
A. 7 cups
B. 21 cups
C. 14 cups
D. 28 cups
The recipe calls for 2 parts borax and 2 parts washing soda for every 1 part of soap flakes. Since Lenny is using 7 cups of soap flakes, he will need 7 x 2 = <<7*2=14>>14 cups of borax.
Similarly, he will also need 7 x 2 = <<7*2=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: D. 28 cups.