Question

p

Answer 1

Let the fraction of rice at $0.8/lb be c (cheap). Then because we only have two kinds of rice in this mixture, we know that the expensive stuff is 1-c, because the cheap stuff plus the expensive stuff must add up to 1.

0.8*c + 0.9*(1-c) = 0.825(1)

0.8c - 0.9c + 0.9 = 0.825

-0.1c = -0.075
c = 0.75

So, we use 0.75 units of $0.8/lb rice and (1-0.75) = 0.25 units of $0.9/lb rice for each 1 unit of $0.825/lb rice. Checking our work, 0.75*.8+0.25*0.9 = 0.6 + 0.225 = 0.825.

0.75 : 0.25 is the same as 3 : 1, so E) is the correct answer.